I found these three this weekend. The top one has no makers mark. Marked 10 on on side and 6 on the other. The next is marked HM inside a B. Last is a Mossberg 230.
Jim
The BHM one id by Bridgeport Hardware Manufacturing Co...
The Mossberg is always a nice find :)
Any chance the top one is 8 and 10 mm ?
I doubt it, since the 9 end looks larger than the 10 end. And the 9/16th on the Mossberg is smaller than both of them.
I say 9 because of the orientation to the opening.
Papaw is right, the larger end is stamped 6 or 9 and since it has a line under the number (6), I call it 6.
Jim