A newly formed company partly owned by two investors who have been trying for months to take over Easco Corp. has made a cash tender offer for 3.2 million shares of common stock of Easco at $20.50 per share.

The tender offer was made by ES Acquisition Corp., formed as a unit of Equity Group Holdings and Clarendon Insurance Co. (Bermuda) Ltd. Steven M. Rales, a general partner in Equity Group, said that "the purpose of the offer is to acquire enough shares which, when added to the shares currently owned by Equity Group and Clarendon, will constitute a majority equity interest in Easco Corp."

Equity Group, whose sole partners are Rales and his brother, Mitchell, has a 17.7 percent interest in the firm, while Clarendon has about a 4.3 interest.

"This is another episode in a continuing struggle between Equity Group and Easco," said Bill Miller, an analyst at Legg Mason. "The two opposing camps are squaring off for control of the company."

Miller said that the offer was "well telegraphed because the company had indicated that they would consider a higher offer above their previous one of $18.50 a share."

Earlier this year, the Rales brothers offered $18.50 a share, or a total of about $170 million, for the Easco stock they did not own. Easco's management turned down the offer as "inadequate," prompting the Rales brothers to propose their own slate of directors and seek to replace management.

In February, the Rales brothers asked Easco for a stockholder list so that they could present their case to the firm's shareholders. Easco had refused to give Equity the list, and argued that under Maryland securities law a company does not have to make its shareholder list available to an investor who has not held 5 percent of the company's stock for at least six months.

Equity Group won its fight to get the shareholder list after hiring D.F. King, a Wall Street investor relations and proxy solicitation firm, which successfully sought other Easco investors to join Equity Group in seeking the list.

An Equity Group lawyer said the company's tender offer is an attempt to go to Easco's shareholders directly after Easco refused to negotiate with the Rales brothers.

"It is a more expeditious fashion to gain control," Rales said.

Easco has not yet announced a date for its 1985 annual meeting, although the company bylaws state that the stockholder meeting is to be held within 15 days before or after April 30, according to an Easco lawyer.