Noted.

No one is claiming anything here. Rather, by a process of deduction, hoping to narrow down, even approximately, the timeframes in which these locks were manufactured.

Something that has become apparent, particularly with the old prison locks, is that very few people seem to have them or, more importantly, know anything about them.

It is partially that aspect, of course, that makes them.so collectable. They were, after all, designed for a purpose totally unique and distinct to any other lock.

The flipside is that it seems incredibly difficult to find historical information regarding them.

It seems likely the blue lock is older but, again, until someone can come forward with literature regarding them (and these locks all would've been in sales catalogues. It is my hope a copy survives because that is where the answers lie), all is conjecture.