The crown/U is the final definitive proof; the crown/G is the proof for rifled barrels, the crown/B means that the proof was done in the finished condition; the crown/E is the proof for express rifle barrels. But the crown/R is the key, as it is the mark for a reproof after repair or alteration; the second set of regular proofs (U-G*) was done at the same time to be sure the alteration did not make the rifle unsafe. The alteration seems to have been reboring and re-rifling the barrel to a larger caliber, done in September, 1928.
The St.m.G means the rifle was proved with a Stahlmantelgeschoss or steel jacket bullet, the number is the weight of the bullet in grams (the heavier obviously for the new larger caliber).
A very interesting and valuable rifle, but I can't come anywhere near putting a dollar value on it. I would think in the medium four figures to the right buyer.
*Edited to note that the second proof set does not include the crown/B or the crown/E. The former was not needed as the gun is obviously in the finished state; the latter was probably omitted because the new caliber was not considered an "express" caliber.
Last edited by James K; July 13, 2010 at 11:25 PM.