Even if she hasn't played a match since Wimbledon, Serena Williams continues to break records but not in the usual way.

Recently, at an auction in New Jersey, a signed rookie card from 2003 of the 23-time Grand Slam champion was sold for a record-breaking amount; $44,280. This sale dethroned the previous highest auction of a women's sports card, a 1992 Mia Hamm rookie card which sold for $34,440.

However, while most sales of this caliber are highly graded—the grade scale is between 1-10, which determines quality of the card, from organizations such as the PSA (Professional Sports Authenticater) - the Serena rookie card is only graded at a 5.

"People are accepting women's trading cards as collectables," Ken Goldin, executive chairman and founder of Goldin Auctions said.