You are correct that there are models with the complete "Potzdam Magazine" engraving. This one is the earlier marking "Potzdam Magaz" with the, as you have stated, the "std" being the contractor. And as you have pointed out, the date could very well be behind the finial of the frizzen spring. I am guessing that this pistol was created 1731 based on the others similar to mine. This would put it at 280 years of age. WOW....
(I do realize there could be a +/- of 10 years in there.)
I am super excited on this find. In further reasearching possible value, the last auction of this pistol (in much poorer condition than mine) by Arms and Armour of England in June of 2006, the hammer price went for 2100 English Sterling pounds.
I have 6-10 additional percussion & flintlock pistols to research so yours and the other knowledgeable member's assistance is greatly appreciated.