Hello Daniele,

IMHO the buckle seems good to me, an original SUN one.

Al the fakes ones I have seen so far have:

a) the shield is in one piece with the buckle (the original ones have the Heuer shield as a separate part, then welded to the buckle);
b) a longitudinal row in the back side of the pin (probably due to casting);
c) being the fake ones in an alloy (maybe brass, not certainly stainless steel) the coating tends to wear prematurely leaving a matt finish.

Cannot answer, instead, if originally the Monza had been released with a black PVD buckle, an unsigned one, or something else..

My 2 cents.

Best.

Gianluca