[Milsurplus] Ring a TU bell?

[Unserviceable but Repairable]

A friend is assembling an estate for sale & in it is this gizmo

> and a small piece of hardware Signal Corps  US Army Tuning Unit  MC-125-A

This wudn't be a plug-in for a BC-746 horsey-guidon-pogo cavalry talky, wud 
it (J. McCarty)?

   tnx the look

          'rm