from all the g/boxes i've seen.........there are no noticeable numbers on them which canbe used to identify a particular make (c52, c151, c56, etc)
u can easily tell the differentiation between a 4 and 5 speed box
some 5 speed n/a starlet boxes even came with e black end cover/cap,
but i have yet to find an easy way to tell a specific box (example ep82 c52 vs ep91 c56)
your best bet is to take it apart to make sure
maybe some1 else has found a way