The .357 SIG cartridge was first introduced in 1994 but Glock didn’t get with the program until 1997. These models fell victim to the same production changes as the ported models and the transitional large frames–very short run before the transition to the Gen 3 frame.
The models 31 and 32 only had two runs produced before the Gen 3 models were introduced. These don’t typically command premium prices on the open market, but good luck trying to track one down!