Linus Yale Sr. Key

[BBE]

That is what is in the picture. I haven't cleaned it but the shinier places are from the lock it operates which I also have. There had been a differing opinion about the key that said it was actually a Linus Yale Jr. but in researching all of the US patents of both gentlemen I think I proved that it is a SR. in an article I wrote.
BBE.

[oldlock]

I would agree LY Sr. This key design was the very 1st version of the pin-tumbler mechanism. The design was simplified down to something close to the pin tumbler locks we know today by LY Sr - however the design was only used for locking curbs into combination vault locks etc.

It was LY Jr who saw the potential of the mass production of such a design for widespread domestic & commercial use.

BWT - the same type of key is also available in Bronze, I have a very worn example.