| System | Period | Rows | What it dates |
|---|---|---|---|
| Christy — the eras of the firm and patent inscriptions (1891 → the 1930s) | 1891 → the 1930s (by patents and the museum record) | 6 | There is no exact “stamp → year” table. What exists are verified museum facts: the Christy Knife Co. was founded by R. J. Christy in 1891, the R. J. C |