The screw holding the rear band in place is distinctive of Czech made rifles and carbines but you do see it on some FN made firearms too.
I had a second run through my book and found a few close examples for Brazil and Uruguay being the Vz-24 "revolutionaire" short rifle and the FN Model 24 short rifles used by these countries respectively.
Another interesting one that comes really close is the Iranian model 30 carbine but that carbine has a band spring retaining the front band.
Brazil, as I understand, locally produced rifles and carbines that closely resembled the FN, DWM, and CZ made contract firearms.
You don't happen to have a copy of a picture with a national flag in it, do you ?