Is There A Reference To Identify How Old Keys Are?

[MilitariaCollector]

Is there some kind of reference to identify how old keys are? I've found a few keys and would like to know when they date from.

 

[AU24K]

I don't know of any web sites that give that information. Perhaps others on this site can come up with something for you. There are many different kinds of keys; there's cylinder keys(like your house keys), skeleton keys, auto keys, etc. I'd like to see some web sites myself!
Scott