A super-rare Allen Iverson card just hit the auction block, but it could very well be out of most collectors' price range ... 'cause someone's already bid $150K!!

TMZ Sports has learned the 1997 Skybox E-X 2001 Essential Credentials Now Iverson piece went up for auction at Heritage Auctions on New Year's Day ... and it's already received an aggressive six-figure bid.

It's a huge number ... especially considering the previous record for an Iverson card sale, according to HA, was $79,200.

That's how coveted the '97 card is to collectors.

Only three of the nearly 3-decade old cards were ever produced ... and only one has ever gone up for sale.

The card -- which features Iverson in a Sixers jersey on the front and his 1996-97 rookie year stats on the back -- is marked No. 2 of three ... and it has a PSA 5 grade, meaning the card shows some signs of wear.

The craziest part ... there's still three weeks of bidding left -- the auction officially closes on Jan. 21 -- and experts tell us it could ultimately fetch up to $200K!