It should be compatible with the first generation pistols. One way to check is to see if the holster is also compatible with the SW99. If that's the case, you should be good to go.
I have a bunch of the 6378 holsters. This holster has a mechanism that fits snugly up against the front/bottom of the frame, in other words where the rail slot is. The Gen 1 frames are unique in this area, being thicker as well as tapered. I'm almost positive your Gen 1 pistol will not fit the 6378 holster.Hi, does anybody know if the Safariland holsters (preferrably 6378 ALS or 7378 ALS) fit the first gen P99? On their website it says the holster are compatible with the P99, but doesn't say if it's gen 1 or 2. I tried emailing them but haven't received a response (I live outside of the U.S. so calling them is a problem for me). If they aren't compatible, can anyone recommend other holsters with automatic retention or tell me if the Safariland GLS Pro-Fit works with the first gen?