Mystery part on G1 Groundshaker - What's it for?

I recently acquired a G1 Groundshaker, a figure I had as a kid and absolutely loved. After getting him in hand again I notice he has a sort of "C" clip bit on the back of the tank that would seem to imply that it was designed to connect to something else such as another Micromaster base or vehicle but for the life of me I can't figure out what it's for and haven't been able to find any info about it online. Does anyone know what the purpose of it is (or was if it was a gimmick that was abandoned but left in the mold's original tooling) assuming it's not just there as some sort of detail?