A 1916 blank back M101 Babe Ruth rookie card is to cross the block at Heritage Auctions.
The lot is valued in excess of $600,000 ahead of the August 27-28 Sports Collectibles Platinum Auction in Dallas.
The lot is one of six known blank back cards showing Ruth and is graded PSA NM 7, meaning it displays only light wear.
It's a legendary rarity that has served as the serious baseball card collector's Holy Grail for generations.
Produced by New Orleans' H Weil Baking Company, it's one of an incredibly scarce series.
Only around 250 cards from the entire issue have ever been submitted to grading.
Heritage comments: "There is only one universally recognized Babe Ruth rookie card, and this is it.
"And while some particularly obscure (and far less significant) issues may exist in smaller populations, this Ruth representation is far and away one of the rarest cards that commonly surfaces in top twenty hobby rankings."
Another 1916 Ruth rookie (graded lower at EX 5) sold for $89,625 at Heritage last year.
Other highlights include a 1953 Topps Willie Mays card, graded PSA Gem Mint.
It's the only card in the entire 1953 Topps series to achieve this grade - remarkable when you consider 128,000 have been submitted over the years.
It's expected to sell for more than $800,000.
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