Blackstone Group Inc. agreed to buy Certified Collectibles Group, which grades and verifies items such as sports trading cards, stamps and coins.

Blackstone said its tactical opportunities group is purchasing a majority stake, valuing the business at more than $500 million. Other investors include Roc Nation, Jay-Z’s entertainment company, and Daryl Morey, president of basketball operations for the Philadelphia 76ers. Certified Collectibles founder Mark Salzberg and Chief Executive Officer Steven Eichenbaum will retain a significant minority stake.

Blackstone, the world’s largest alternative investment firm, has wagered on companies focused on software, social gaming, defense and health care through its opportunistic group, under the leadership of David Blitzer. The unit recently made bets on telecommunications provider Hotwire Communications and security company FireEye.

The group’s funds posted gains of more than 15% in the first three months of 2021.

In the Certified Collectibles deal, Blackstone aims to boost the company’s growth, allow it to hire and train new employees and develop its online presence. The collectibles group started by evaluating coins 35 years ago and has moved into areas like comic books, bank notes, magazines and sports cards.

One of the company’s main competitors in the collectibles-grading industry, Collectors Universe Inc., was taken private earlier this year by Cohen Private Ventures, which invests the personal capital of hedge fund billionaire Steve Cohen, along with Dan Sundheim’s D1 Capital Partners and sports card collector Nat Turner.

This article was provided by Bloomberg News.