Originally Posted By: ellenbr
Geno:
Is the tube pic with "HK"/"KH" from the same longarm as the receiver with the "AG" stamp?

Yes. There is the same mark is on the bbls flats, not on pic.
I recalled I saw the same mark on one more post war gun and there was not maker name as well.
I got a thought maybe this A-G means A.G. - joint-stock company/corporation? By s/n's I'd say this maker started to make guns just after the war.

Geno.