I can only add that H&H may have used a smaller set of stamps for their S51 marking in the earliest days. I have a very well used butt here stamped "DP" which has the following rather unique characteristics:
1. Beech like post war Mk2 stocks
2. Recessed for but marking disc, which was fitted at one point from the screw thread marks in the hole. The wear around the hole makes it obvious that the disc was removed long before this left service however.
3. Two scope SNs stamped in the wrist, one a 3--- number the other a 5--- number.
4. Below those numbers is a mark I can't ID that looks like a large zero with a smaller 'o' or similar (C, G?) inside it. This is a very faded and worn over mark, contemporaneous with the scope SNs from it's appearance.
5. No holes for cheekrest screws.
6. Very faint smaller than usual "S51" stamped in the usual place. Not as deeply struck as usual ones.
7. No maker's codes present, possibly worn or scraped away in refinishing during overhaul. There are what I consider scraper marks on the butt.
8. No rifle SN on the tongue of the butt.
