- Document the object
- Classify material and use
- Read marks and model evidence
- Check originality and safety
- Compare references and sold examples
- Create a permanent record
Start with an evidence sheet
Use exact identity, originality, completeness, condition, documentation, demand, and logistics to estimate value conservatively. A good evidence sheet includes overall photographs, every mark, dimensions, weight where safe, materials, moving parts, paint and decals, repairs, dealer or farm history, associated manuals, and the circumstances in which the object was found.
Separate observation from interpretation
“Green paint,” “cast number 1234,” and “dealer decal from Lima, Ohio” are observations. “John Deere,” “1930s,” and “used on the Smith farm” are interpretations that require sources. Keeping those layers separate makes later corrections easy and prevents a family story from becoming an unsupported sales claim.
Use multiple reference types
- Period catalogs and operator manuals
- Parts books and service bulletins
- Dealer advertising and city directories
- Patent drawings and trade literature
- Museum, archive, and historical-society collections
- Exact completed marketplace sales
Do not let value drive identification
The most expensive-looking answer is often the least reliable. Identify exact maker, model, version, originality, condition, completeness, and provenance before estimating value. Large machinery and dense iron may have significant local interest but limited shipping markets.