NHL Legend Mike Bossy -- My Super Rare Puck Is On eBay ... And I Want It Back!!

NY Islanders Hall of Famer Mike Bossy is eyeing a legendary NHL puck on eBay, but refuses to pay a dime -- 'cause in his mind he's the rightful owner, and he's pissed someone's trying to sell it off.

Here's the deal ... in 1981, Bossy scored 50 goals in 50 games -- a feat only accomplished by 4 other players -- but about 30 years ago the treasured 50th puck slipped out of his hands.

We spoke to the eBay seller, Jake Jacobson ... a HUGE Islanders fan and former swim coach, who claims he ended up with the prized puck when Bossy's young daughter gave it to him as a thank you for her swimming lessons.

A couple years ago he contacted Bossy and offered to return it, but claims Bossy "didn't really seem interested." He says Bossy offered him a signed stick and that's about it. "He couldn't even meet. It just wasn't a good offer."

So, now Jacobson's gone the eBay route, and Bossy's ready to drop the gloves. The Hockey Hall of Fame and Museum -- which also wants the puck -- tells us, "Mike's position is, if the puck was mistakenly given to the seller, it's his rightful property. He shouldn't have to buy it back."

Bossy hasn't lawyered up, and Jacobson's pressing forward with the auction ... which ends Tuesday. Here's the thing ... his opening bid is $850, and he has ZERO offers.