Jim Brown Championship Ring Stolen? -- Auction House: It's NOT Stolen Property

Jim Brown's 1964 Cleveland Browns championship ring is 100% NOT stolen property ... despite allegations from the NFL legend ... this according to the auction house that's selling the item.

TMZ Sports spoke with Josh Evans -- founder of Lelands Sports Auction House -- who tells us he originally obtained the ring in 1998 from a family member who got it as a gift from Brown himself.

Evans says at the time of the purchase, the item and the seller were vetted -- and the Auction House determined the family member was the rightful and legal owner of the ring.

Evans says ... after he purchased the item in '98, Brown himself visited Evans at a trade show and asked if he could check out the ring. Evans says Brown was polite during the interaction, but was clearly upset the ring was up for sale.

Eventually, Evans says the ring was sold to a collector ... who has gone back to Evans to sell the ring at auction ... which is set to end on July 25th. The ring is expected to fetch more than $250k.

But Brown is clearly upset about the sale -- telling TwinCities.com the ring was "stolen from me in the '60s" ... and adding, "Whoever got it should know that I didn’t give it up."

Evans says he believes Brown is misdirecting his anger -- telling us he thinks the NFL legend is simply disappointed that a family member would sell such a treasured item.

Evans says he's dealt with several athletes who make similar allegations -- and says they're usually upset that "things got out of their control. They're embarrassed or angry at family members and they lash out."