That’s a great find Adrian 🙁y):
I’ve got a couple of those boxed away in the attic somewhere, but mine aren’t lock or safe related- that bit does make yours a lucky find. I think the blocks in general are possibly more common than some might think- there are a quite a lot of them out there and people collect them pretty much like they collect anything else.
Yours is possibly rarer than some as it looks typical of those used for higher volume printing like newspapers etc and has the copper plated face. I think most were heavy base metals like zinc with the copper plating usually used on higher production blocks.
I’m no expert though, so as to rarity and whether it’s genuine or fake you’d have to join an old printing forum to know for sure, but it’s just one of those curios I can’t see anyone trying to copy- when you consider the complexity of making them it’d never be worth the time and trouble. They might consider faking one for a newspaper’s first issue or a famous news headline if the potential value was high enough, but I can’t see it for a Yale padlock advert- I think you can safely assume yours is genuine! 🙁happy):
