What the assembly is, is your lower engine mount, there is a rubber mount underneath that cap where the two bolts are. The continuity strap is to connect the ground path from the mount bolt back through to the yolk in the front. That ground should be under or on top of that large washer underneath a hex head of that large bolt but the head appears to be corroded away probably because the ground was never connected there. This may have been this way from when the engine was new or someone put mounts in it at sometime and botched it. Either way, I would not worry about it, the thrust on that mount is towards the front so it's not going anywhere.