Recently a model 15 with a canteen snap sheath was offered on eBay was dated in ink on the back as February 1960.
We know Heiser became HKL and acquired a Randall stamp for their sheaths.
As We know, the Astros went into development in early and mid 1960, with the astronaut knives being shipped in mid 1960. I have not seen the back of any of the sheaths that went with the astronaut knives, but I think it would be safe to say that they probably had the Randall stamp on the back of them instead of the Heiser stamp. Has anyone observed the back of any of those knife sheaths sent to NASA?