Unlike many/most other models, those variation numbers don't run consecutively on the M25 variants. The 25-2 is a 45ACP Target revolver; my recollection is that the 25-3 was a limited production 45 Colt with a cylinder shorter than most 45 Colts would have (maybe the same as the 45ACP cylinder, but rechambered; not my knowledge set). IIRC, the 25-4 was some kind of commemorative, and the positive response to the 45 Colt variants resulted in the 25-5. The production periods overlap, and thus you have this confusing set of information.
My recall of the details may be wrong, but I think I am right in general, and that if you search the forum you would find some very detailed answers.