The Model 41-1 in 22 short was introduced in September 1960 and discontinued in 1973 with only about 1,000 units produced. To convert a dash 1 to a standard model 41 only five parts are needed:
1. Any model 41 barrel chambered in 22 long rifle
2. A steel slide to replace the alloy dash 1 slide
3. A standard weight main spring
4. A model 41 22 long rifle magazine
5: A model 41 slide stop / ejector
You have already, in my opinion, the best model 41 LR barrel. I’ll assume the other parts have been installed to convert your pistol to a standard model 41. The letter will tell you only that it was shipped as a dash 1, the date shipped, and to who it was shipped to. Even if it was unlikely sold to some famous person, you would still have to restore it back to dash 1 configuration to have any increased value. Enjoy it and shoot it often!