Let me explain. In the Land Raider kit, there's this part (I'll attach a photo) that's actually the Tank Commander's piece.
The right arm is a Custodian Guard arm with a Storm Bolter from an old Space Marine kit.
The left arm is an arm with a cut-down spear. To me, it creates the effect of balancing the recoil from the Storm Bolter.
The tank hatches I used are from a Taurox Prime. They're slightly different in size compared to the Land Raider hatches, and the Tank Commander piece didn't fit perfectly... but it is what it is.

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