Okay, I guess a few hints might help then? lol... I thought it might have been easier to guess this one since I had talked about it quite a bit on the forums previously (I thought at least?)
The item I went to go pick up I was not buying from Bruce, but I did get it from a guy who lives about a half an hour away from Bruce's neck of the woods in New Jersey, so I figured I'd stop by and visit on my way through. That is why he is disqualified from guessing! lol.
You are correct in that it is big and required a trailer to go pick up.
This particular attachment *should* work with my Bolens (I hope!

Yikes!) however it was NOT made by Bolens. It *could* have been offered for sale at the time by a Bolens dealer to go with a tractor, but I'm not 100% sure. That you WOULD have to ask Bruce about (since he was a tractor dealer for a number of years)...
This attachment is engine driven (unlike the Brinly sweeper I got before that is run by just towing it.)
It is nothing for a large frame Bolens (as I don't have one). I only own one measly tube frame right now (unlike just about everyone else on this board it seems!)
It is indeed NOT a piano! We have our first winner to guess what it is NOT, I guess then?