Building Breacher Squad Marines, and What To Do With Part 52

I recently bought the Breacher Squad boxed set, including the marines and the upgrade frame. I really like the look of these squads, even though they are probably more suited to the close confines of Zone Mortalis, I still feel that they have a good role to play in regular Horus Heresy games. The invulnerable save gives them and edge to stay on objectives and also to advance under otherwise horrendous fire. 

For this particular squad, I am aiming to build them up as Iron Hands. The first miniature, and squad sergeant is pictured below. 

Here I have done a simple head swap from the Praetor character to make him look a lot more like an Iron Hands character. The shoulder pad is also a Forge World resin upgrade. And yes: I know it should probably be on the other side, but the shield made it too bulky to fit, so too bad. He is armed with a power fist which is (presumably temporarily switched off) gripping a melta bomb ready to be attached to some enemy armour. 

The Breacher marines themselves are very easy to work with and I am impressed by their quality. They come with a lot of left over pieces as well. But the parts labelled 52 puzzled me a lot at first, as shown in the second image.

These parts are not mentioned in the slightest in the instruction booklet. It took me a little while to puzzle this one out. They are arm guards, or bracers. Effectively these can be used on other armour marks to make them more convincingly look like Breacher Squad members. I think I might use them anyway as conversion pieces on other armour marks to help pick out squad sergeants or marines who otherwise have artificer armour or similar. They are not much use with the marines supplied in the box since they already have these parts moulded on to them naturally. Hence I think this is mostly for Mark 4, 5, or 6 to take advantage of in my opinion. Puzzle solved!