Auction House -- Sharon Tate Ring Is LEGIT, We Have Proof

The auction house behind the controversial Sharon Tate "engagement ring" tells TMZ ... it has written confirmation from Roman Polanski verifying the authenticity of the jewelry ... and claims it WILL NOT yank the item from the auction block.

TMZ broke the story ... Sharon's sister Debra insisted the ring wasn't Sharon's "official" engagement ring -- and also claimed it was NOT on her finger the night she was murdered by the Manson family.

But a rep for the auction house GottaHaveRockAndRoll.com tells us, "It was speculated that the ring was on Sharon Tate's finger at the time of death but never confirmed so we do not dispute Tate's sister Debra's claim."

The rep adds, "We do, however, have photographic proof of Tate wearing the ring (seen above) and written confirmation from Roman Polanski stating that this was, in fact, the engagement ring that he gifted to his then-fiancee, Sharon Tate."

"Gotta Have It! along with the consigner are 100% confident in the authenticity of the ring. There are no plans to pull the ring from the Gotta Have Rock and Roll Pop Culture auction as the consigner, who maintains ownership of the ring, is committed to its sale."