pontil mark is 5/8 of an inch not quite perfectly round and the 1,5 inches outside of that is ground and polished. To me the capitol G in the sig and the way the T is crossed on the right hand side is identical to some examples I have seen on the net. The piece was bought at an auction I work for, the piece was in a box in the attic and was wrapped in a 1962 news paper. If the sig was forged it would have been before then.