One thing to look for in general with marine arms is similarities.
GW puts the same “tell” on both arms more often then not.
For example, there should be a pair of sternguard arms both with cords tired around them.
And a pair with bulky riveted forearm guards.
If you look at the sprue pic on
GW’s site, the matched arms share a same letter code. So 76A goes with 75A
Hope that helps.