I have the M57 Zastava/Yugoslavia [Serbia] version...It has a longer grip and magazine and holds one more round than the Russian/Chinese versions...And it has been fitted with a thumb safety (which needed some work, but that is detailed on the Web).
I like it. Typical Browning design, chambered for the 7.62 x 25 Tokarev round. Sturdy, no-nonsense, and has several 'improved' features that the M33 or M20 do not have.
And relatively cheap by today's standards.