Unlocking The Past: A Collector’s Guide To Identification Of Antique Plow Parts

Antique plow parts may look like a jumble of iron, steel, and wood to the untrained eye. To collectors and appraisers, however, they are a readable archive of rural technology, regional industry, and workmanship. This guide shows you how to identify and date plow components with confidence: what the parts are called, how they differ by era and maker, which measurements matter, and how to handle them ethically to preserve value.

Plow Types and Anatomy: Know What You’re Looking At

Before you can identify an individual piece, orient it within the plow’s overall system. Most 19th–early 20th century American plows fall into three broad categories:

• Walking plows: Human-guided, with wood handles and often a simple beam. Early and common for small farms.
• Sulky plows: Horse- or tractor-drawn with an operator’s seat and wheels; more complex frameworks and multiple adjustments.
• Gang plows and hillside/reversible plows: Multi-bottom or reversible designs for specialized soils or slopes; rarer and mechanically distinctive.

Key components you will encounter:

• Beam: The main longitudinal member. Early beams are wood (oak/hickory), later beams are steel.
• Frog: The central casting or forging to which the share, landside, and moldboard attach. Maker’s numbers are often on the frog.
• Share: The cutting blade at the bottom that slices the soil. Replaceable and thus commonly found loose.
• Moldboard: The curved plate that turns the furrow. Can be wood-faced, cast iron, wrought/steel plate, or pressed steel depending on era.
• Shin: The forward upper portion of the moldboard, a high-wear area.
• Landside: The flat plate running along the uncut soil, stabilizing the plow.
• Coulter: A vertical cutting element ahead of the share—either a knife (slit coulter) or a round disc.
• Jointer or trash board: A small auxiliary board ahead of the moldboard that flips surface debris.
• Clevis or hitch: Adjustable connection for the draft animals or drawbar; often with graduated holes.
• Handles: Usually wood on walking plows; species and joinery can indicate age and quality.
• Standards and wheels: On sulky/gang plows, hold depth and alignment.

Terminology matters. For example, what some call a “plow blade” is typically the share; the “bottom” refers to the full assembly of frog, share, moldboard, shin, and landside.

Materials and Manufacturing Clues: Dating by How It’s Made

Materials and fabrication techniques changed noticeably between about 1840 and 1930. Those shifts are your first dating clues.

• Wood and wrought iron (pre-1870s, with overlap): Early beams and handles are wood; iron components may be blacksmith-forged with hand-hammered surfaces and tapered rivets. Wrought iron shows fiber-like grain in fractures and produces long, straight, relatively quiet sparks in a spark test.
• Cast iron components (mid-19th century into early 20th): Frogs and some moldboards were sand-cast. Look for parting lines, draft angles, and angular sand texture. Cast iron spark tests produce short, red-orange, non-branching bursts. Cast surfaces may be pebbly; chilled casting produces a glassy-hard skin.
• “Chilled” cast iron (late 19th century): Associated with brands like Oliver. Contact surfaces (shares or moldboards) were cast against a cold iron mold to harden the face. You’ll see a smooth, dark, wear-resistant surface on one face and normal cast texture on the other.
• Steel plate moldboards (post-1870, common by 1890s): Rolled or pressed steel with uniform thickness and, on later models, a smooth, machine-pressed curvature. Riveted or plow-bolted to the frog. Hammer marks on earlier steel indicate hand-forming.
• Hardware evolution: Square nuts and domed square-head bolts dominate 19th century; hex nuts become common in the early 20th century. Countersunk “plow bolts” with oval necks that lock into square holes appear widely in the late 19th century. Coarse threads (USS) precede finer SAE threads on later machinery.
• Finish: Early parts may have black japanning, oil blackening, or simple linseed/oil finishes; mid- to late-1900s pieces may show factory paint colors tied to brand identity.

Caution: Perform spark testing only with appropriate safety gear, outdoors or in a shop. A magnet won’t differentiate iron from steel; both are ferrous.

Maker’s Marks, Patents, and Part Numbers: The Language of the Foundry

Many plow parts are signed—sometimes boldly, sometimes cryptically. Train your eye to find and interpret markings.

Where to look:

• Frog: Common location for cast-in maker’s name, part numbers, and pattern codes.
• Moldboard and landside: Edges or underside often carry stamped or cast numbers.
• Share: Replaceable shares typically have pattern numbers and sometimes a brand; numbers may be worn away at the cutting edge.
• Coulter hub and brackets: Embossed initials or patent dates occur here.
• Hitch/clevis: Graduations, maker initials, and town names can appear on faces.

What you may see:

• Company names and towns: Deere (Moline), Oliver (South Bend), Syracuse (New York), Vulcan (Evansville), International Harvester and McCormick-Deering, among others. Location helps triangulate era and distribution.
• Patent dates: Often a range like “Pat’d Apr. 5, 1887; Aug. 12, 1891.” These give you a “not earlier than” date; production commonly follows within a decade or two.
• Part and pattern numbers: Sequences like “MB-5,” “No. 40,” or alphanumeric codes. On some brands, share numbers correspond to specific frog patterns—critical for matching a bottom to the correct share.
• Process descriptors: “Chilled,” “Steel,” “Solid Comfort,” and other trade names or slogans can anchor the maker and timeframe.

Unmarked parts aren’t rare. In those cases, identification shifts toward geometry, hole patterns, hardware type, and material analysis.

Measuring and Matching: How to Identify Unmarked Parts

When marks are absent, measurements become your vocabulary. Consistent, replicable dimensions let you match parts across piles of iron.

Core measurements:

• Hole pattern: Count the number of bolt holes and record center-to-center spacing along and across the part. Note whether holes are round or square, and whether they are countersunk and of what shape (flat vs oval).
• Overall dimensions: For shares, measure point-to-heel length and wing width. For moldboards, measure overall length and height, and note the shape of the leading edge.
• Curvature: Use a flexible curve or contour gauge to capture the moldboard’s profile at the shin and midline; trace onto paper for a template.
• Thickness: Use calipers to check plate thickness on moldboards and landsides; chilled edges may be fractionally thicker or harder.
• Hardware size: Identify bolt diameter and thread pitch where hardware survives. Old plow bolts may be 7/16" or 1/2" with coarse threads.

Diagnostic features:

• Frog interface: The frog’s bolt pattern and seat angles are highly brand- and model-specific; a match here is the most reliable way to pair shares and moldboards.
• Landside geometry: Some makers favor long, straight landsides; others use tapered or stepped designs.
• Coulter type: Knife coulters with forged shanks skew earlier or for stony soils; disc coulters with adjustable arms become widespread later.
• Countersink style: Oval-neck plow bolts seat in square holes; a mismatch between hole shape and expected bolts can signal a non-original pairing.

Practical process:

1. Clean just enough to reveal edges and holes. Avoid grinding; use plastic scrapers and light oil.
2. Record all measurements and sketch the hole pattern with a ruler and grid paper.
3. Note wear and repairs. A newer share on an older frog is common; treat each piece separately.
4. Compare against a known pattern library if you maintain one. Many collectors build binders of tracings by brand and model.
5. When in doubt, mock up: Temporarily assemble the parts on a bench to confirm alignment and seat angles.

Recognizing replacements and repairs:

• Different metal color/texture and fresher edges on a share typically indicate replacement; this is normal and not necessarily a value detractor.
• Torch-cut modifications to holes or slotted holes often scream “field repair,” which affects originality and sometimes value.
• Welding on cast iron frogs or moldboards is a later intervention; look for nickel-bronze or arc weld beads.

Condition, Conservation, and Ethical Restoration

Collectors and appraisers balance aesthetics, preservation, and originality. The goal is to stabilize and present, not to erase history.

Assessing condition:

• Wear vs. corrosion: Soil polish and honest wear at the shin, share, and landside are expected. Deep pitting elsewhere indicates long-term exposure.
• Completeness: A “complete bottom” (frog, share, moldboard, landside intact with appropriate bolts) is more desirable than baskets of loose parts.
• Original finishes: Surviving paint, japanning, decals, and stenciling add value. Sooty black surfaces may be old oil/coal soot layers, not dirt alone.

Conservation best practices:

• Dry cleaning first: Use soft brushes, wood or plastic scrapers, and vacuum to remove loose dirt.
• Rust stabilization: Light mechanical cleaning with brass brushes, followed by a rust converter (tannic acid-based) used sparingly and reversibly. Avoid harsh acids or electrolysis on historically finished surfaces unless you’re treating active corrosion and documenting the process.
• Protective coatings: Microcrystalline wax (thinly applied and buffed) provides a stable, reversible barrier. Light machine oil can darken surfaces; use with care.
• Wood care: Consolidate loose fibers, clean with mild soap and water (sparingly), and finish with a microcrystalline wax or a traditional oil-wax blend. Avoid thick varnishes or polyurethane that create a modern look.
• Hardware: Preserve original bolts and nuts. If replacements are needed for assembly, use period-appropriate square nuts and plow bolts, and keep originals labeled in a bag.

Restoration cautions:

• Do not grind or belt-sand the working faces to a shiny finish; you’ll erase tool marks, maker’s stamps, and dimensional integrity.
• Avoid sandblasting original paint and decals. If you choose to repaint a non-collectible work display, clearly document and date the restoration.
• Reversibility and documentation are key. Tag interventions with notes that can travel with the piece.

Storage and display:

• Keep relative humidity moderate and stable (roughly 40–60%).
• Use padded supports to prevent stress on fragile castings.
• Avoid direct contact between dissimilar metals if long-term storage is planned; insert inert barriers.

Rarity, Regionality, and Market Value

Value flows from a mix of age, completeness, maker desirability, and scarcity.

• Early and transitional technology: Blacksmith-made or early factory pieces that bridge wood, wrought iron, and cast iron eras are scarce and prized.
• Maker prestige: Firms with strong brand stories—Deere, Oliver, Syracuse, McCormick-Deering—draw sustained interest. Local foundries with limited distribution can command premiums regionally.
• Specialized designs: Hillside/reversible bottoms, prairie breakers with massive shares, and left-hand plows (mirrored bottoms) are less common.
• Originality: A bottom with matching frog, moldboard, landside, and a period-correct share is more valuable than an assembled set with mismatched patterns.
• Provenance: Farm records, period photos, and family histories enhance appraisal outcomes.

Remember that detached parts sell differently than complete implements. A rare frog or an early chilled share can outvalue an ordinary complete bottom, depending on the collector base seeking that pattern.

A Practical Checklist for Identifying Antique Plow Parts

• Name the part: Share, moldboard, frog, landside, coulter, etc.
• Record marks: Maker, town, patent dates, and all part numbers.
• Measure hole patterns: Count and center-to-center spacing; note hole shapes and countersinks.
• Note materials: Cast iron vs steel; chilled surfaces; wood species for handles.
• Document hardware: Bolt/nut types and sizes; square vs hex; thread pitch if possible.
• Capture curvature: Trace moldboard/shin profiles; note frog seat angles.
• Assess wear and repairs: Look for grind marks, welds, torch cuts, and replacements.
• Photograph and sketch: Include scale reference; annotate measurements.
• Stabilize condition: Dry clean, conserve, and store properly before further handling.

FAQ: Antique Plow Part Identification

Q: How can I tell cast iron from steel on a plow part? A: Visual texture and spark testing help. Cast iron shows coarse sand casting texture, often with thicker sections and short, dull red sparks. Steel plate moldboards have rolled surfaces, thinner uniform sections, and bright, branching sparks. Use spark tests with proper safety.

Q: Do patent dates equal the manufacturing year? A: No. Patent dates indicate “no earlier than” production, but parts were often made for years or decades afterward. Use patent dates together with hardware style, materials, and maker addresses to refine the window.

Q: Will repainting increase value? A: Usually not for collectors and appraisers. Original finishes, even fragmentary, are preferred. Repainting may be acceptable for educational displays, but it generally reduces collectible value. Stabilization and preservation are safer choices.

Q: What if my share has no numbers—can I still match it? A: Yes. Measure the bolt pattern, hole shapes, and overall geometry, and compare them to your frog’s seat. A match at the frog is most decisive. Templates of known patterns are invaluable when numbers are gone.

Q: What is the frog, and why does it matter? A: The frog is the central casting/forging that ties the bottom together. Its bolt pattern and seat angles determine which shares, moldboards, and landsides will fit. Identifying the frog often unlocks the entire bottom’s identity.

By approaching antique plow parts methodically—combining anatomy, materials, markings, and measurement—you’ll turn seemingly anonymous iron into documented, dateable artifacts. Preserve the evidence you find, take measurements you can reproduce, and let the parts tell their story.