Crown Books Corp. has sold its entire investment in May Department Stores Co. for a $500,000 profit, the company told the Securities and Exchange Commission yesterday.

Two months ago, Crown disclosed it had purchased 370,700 May shares -- nearly 1 percent of the company -- for $15 million. That set off speculation that Crown, its parent Dart Group Corp., and its chief owners, the Herbert H. Haft family, might try to take over the much larger St. Louis-based retailer, which owns The Hecht Co.

Yesterday, however, Crown said that after acquiring an additional 70,000 shares for $3.3 million in late February, it sold all of its shares a month later for a total of $18.8 million.

May Co. officials yesterday said they had no information "as to other holdings of the Haft group."

Analysts speculated that Crown sold its holdings after it became clear that May intended to fight any takeover bid. Shortly after it became aware of Crown's holdings, May bought out its partnership interest in a Los Angeles apartment complex for stock, giving its former partner about 5 percent of its shares. May's stock closed yesterday at 46 7/8, up 1/2.