I have a FN1900 as part of my collection of 32s. A most unusual gun, the barrel is underneath the recoil spring. The fit between the recoil slide and frame is very close, and the whole gun has a massively over engineered feel to it. It was JMBs first semi auto pistol and I believe the gun that the 32acp round was originally developed for. it’s interesting if you look at the FN1900, the Colt 1903 and the FN1910 to see how quickly pocket pistols developed in such a short time.