G'day Marty,
I've got no knowledge of the anniversary machines except for having dismantled two for parts - and neither of them had that 'thing' but they both had bits missing and one didn't have a deck.
I've had a bit of a stooge around the interweb and just been outside to look at the remainders of mine. There is a u channel across the chassis plates about where your fingers are in the photos. On mine the channel has a slot in it such that the end of the 'thing' your holding might slot into it? Also, I noticed on a very blurred copy of an IPC there is a largish spring attached to the rear panel near the tow mount. Could it be that the other end of the spring attaches somehow to the hole in the 'thing' in the photo? And then it would act as a tensioner.
Not sure if I'm helping or not.
Cheers,
Last edited by prd; 22/10/16 07:07 PM.