Irwin L. Jacobs bid for a Texas oil and gas firm.

Pioneer Corp. said it received an unsolicited takeover offer of $23 a share from Minstar Inc., the company headed by the Minneapolis financier. An investor group led by Jacobs currently owns about 4.6 million shares of Pioneer common stock, or 14% of the 33 million shares outstanding. Under Jacobs’ offer, the cost of buying the remaining shares would be $653.2 million. Amarillo-based Pioneer said it was reviewing the offer and planned to call a special board meeting to consider the proposal. In another development, Jacobs said that Minstar had received an unsolicited offer of $200 million in cash for the bowling operations of its AMF Inc. unit. Jacobs did not identify the bidder.