This is actually a Krieghoff Neptun. Sempert disappeared from the firm name when it relocated to Ulm after WW II. It is a gun I purchased in Germany about three years ago and it has been at my gunsmith's since then. It has had the rifle barrel opened up from 7X65R to 8X65R and the stock operated on to remove the unsightly "hog back" (Schweinsruecken).
I can't give you all the particulars, since I don't have it here, but it was made in the 60's, completely by hand, has the side lever cocking device for the rifle barrel with the slide safety on top of the stock wrist where it belongs, the barrel length is 25", the length of pull is 14", the drop at the comb 1 3/4", and the drop at the heel 3".
The last time I was in Germany, I had the opportunity to take it to the range and fire it both at stationary rifle targets and at clay pigeons on the skeet range. It performs flawlessly.
I now have the import certificate and expect to have it in my hands before too long.
The Neptun Primus has hand detachable locks and this one has the faint outline of a screw head just discernable under the engraving on the left lock plate. Some of the Neptun Primus models had a hand detachable trigger plate action for the rifle barrel as well. The have a little lever directly in front of the trigger guard.