| System | Period | Rows | What it dates |
|---|---|---|---|
| Gillette Canada (Montreal) — numbers with the prefix C / PC and without a prefix; the 1Z series | “The Montreal plant began low-volume production ca. 1906-04-??, increasing through 1907”; in WWI most razors for Europe were made in Canada | 6 | KEY POINT: no year can be derived from a Canadian number. Verbatim: “The serial numbers for known Canadian razors are somewhat spotty and even contrad |