This should be easier to determine than the origins the ancient pin lock. I have noticed that with few exceptions, safe deposit locks in the US are lever tumbler with a flat lever key. It appears the flat key style was in response to the Hobbs pick, but I have never found any proof of this. Also strange that while the pin tumbler become for most locks, the lever style was retained in the banking industry. Size constraints may have been a factor, but I am thinking the flat key was the deciding factor. Doug