Just a day into its online auction and a rare Honus Wagner baseball card has already reached $643,078.

The card, graded a "very good" 3 out of 10, is expected to have achieved $1.5m by the time bidding ends on April 19.

A Honus Wagner with a similar grading sold for $145,000 in 2000, while another made $950,000 in 2008.

T206 Honus Wagners, produced by the American Tobacco Co. for its cigarette packs in 1909, are regarded as the pinnacle of baseball card collecting.

Honus looks on course to surpass his $1.5m estimate

The Wagner forms part of a 528 card collection of T206s going under the hammer; they have been consigned by an anonymous collector.

"I've been doing this for 26 years, and it's got to be the highlight of my career," Bill Goodwin, the president of the auction house, told Bloomberg.

"Grading companies have graded 43 Honus Wagners, but only five have been graded in higher condition," he added.

The card's value is a testament to its rarity. Around 50 specimens are thought to exist, following the Pittsburgh shortstop's complaints of the use of his image, which resulted in a brief print run of at most 200 cards.

The most expensive specimen is currently the Gretzky T206 Honus Wagner. Graded an eight out of 10, the card was bought by Canadian hockey star Wayne Gretzky in 1991, before being sold for $1.26m in 2000. It last changed hands in 2008 for $2.8m.

A unique example of the Honus Wagner will also appear at a sports memorabilia auction in New Jersey, US, which begins on April 16.

It contains the one-off date stamp of "Oct 16 1909" on the reverse, and carries an estimate of $300,000.

Paul Fraser Collectibles will keep you up to speed on both auctions as they progress.