M-135 Gun Mount

I have a gun mount on my USMC M-135. Process of a frame up restor. I'ver removes the ring and mounting tubes. I have a question. On the forward side of the ring , there is a bracket that is bolted to the tube bracket, what is this bracket for?
Have attached two photos - any ideas

Could that be for the magazine holder?

Sorry,
Forgot another shot, which could help

I don't think so, I have a skate that is attached to the ring, which holds the bar and cradle, and in turn holds the gun and the ammo box. If you have a copy of the June 2005 issue of the MV Magazine, BMG's adv, showes the skate and the cradle is similiar to the one he shows in the adv.

But it coud be to hold a spare ammo can, what do you think?