Mike,
A very interestng topic. It looks like four different variations. I have gone through my archives and internet posts to see if I can find more examples. Its not easy. I have come across:
A 1906 in the 38000 range
A 1906 9mm (serial number unknown)
and a gun in the 74000 range which looks like the eagle may be engraved.
I think I see at least one more variation in these examples.
It would be interesting to establish a gallery of American Eagle chamber stamps, if people with American Eagle Lugers would take good, sharp, big pictures of their chamber Eagles and post them here. The pictures will be the most interesting and useful if the stamps are not whitened.
I wonder if the Eagle stamp evolved over time, if new stamps were made as they wore out, or if they had several different stamps which were used concurently?
--Dwight