Rich,
This is a very attractive piece. How long is the barrel?
By the looks of it, I Think it was full -stocked at one time, and likely made into half stock when converted.
I see a screw where the sling button or sling swivel may have been fitted behind the t/guard. Is there any evidence of a sling near the foreend tip?
Most Germanic half-stocks has such a sling, plus two close positioned pipes, (Entry and one just ahead of it), plus a horn end -cap.
If yours has no sign of these, I think it will be for sure a cut -down stock.
If the rib is loose and will come off easily, there may well be signs of barrel lugs and sling lug hiding under it.
I too have one with a shallower than what we think usual buttstock, (Top to bottom) but it still fits well in Geo. Shumway's list of measured examples.
It's a lovely piece!
Have you any ideas on the wrist escutcheon? Is that a Ducal coronet?
Congrats on it Rich!!
P-B.