No problem, glad to help.
If they are already off the sprues, look at the detailing.
The “A”s have a little 3 slot vent on them
“B”s have a tetris like block pattern, but smooth
“C” have a little rectangle with two sockets in it.
“D” is very close to “B” but has a small raised button on one of the segments.
This is for the tactical sprue. Can’t speak for the sternguard one, as I’ve already cut most of mine. But they’ve been using this trick to pair arms since 3rd edition.