Have the gun again and checked the markings. The actual stamp under the barrel reads:
PAPP.16__65.4,75S.P.28,5 BL.
I bought the J.P. Sauer & Sohn book by Arfmann but didn't learn anything new on the gun. Emailed SigSauer and any records from the time were lost in fire and/or bombings.
I measured the LOP based on front trigger to midpoint of butt, this came out to approximately 13 3/4.
The drop at heel measures approximately 2 3/8.
A collector friend of my brother-in-law said its condition is 85%.
Thanks again for the interest.
