What Burnt Servo said. Belgian guns, the copies were made by the hundreds of thousands in many hundreds or thousands of little family owned machine shops cranking out guns. The plus is these private made obscure guns were required by law to be proofed in order to sell on the market, that's great and I love Belgian made revolvers due to that aspect but it does not help in the parts and maintenance aspect.
Again like Burnt Servo said, even with the big name producers, it's possible from gun to gun that you will require to fit parts with a lot of personal work.
From my personal experience, the concept of parts interchangeability is laughable at best.