I noticed your pistol has 1 or 2 screw holes on the top rear of the right side of the frame. The other pistols shown don't have them. It may have had a Wonder-Sight after-market adj. sight on it. Wonder sights are still being made, believe it or not, and would be a period-correct addition to your pistol. An internet search should lead you to the mfgr's site. Beautiful pistol == I hope this helps!
John