Collector technical vocabulary
Cam spring
Cam-spring form is a useful insert clue. Glen documents the Canadian sequence as humped to around 1957, narrow/straight from around 1957/58 to about 1970 (with examples into 1971), then widespread from around 1970 onward.
Source and interpretation
Sources: Glen's Zippo Page — Historical bottom-stamp, case/insert construction details, Canadian dating chronology, and transition research
This feature is supporting evidence alongside the case stamp, insert and other manufacturing clues. An individual component can be repaired or replaced.