The Beverly Hills-based savings and loan announced an offer to exchange 750,000 shares of newly issued common stock for $15 million principal amount of subordinated debentures due 1994. The offer will increase Columbia's outstanding common stock by 10% if it is fully subscribed. Columbia also said its fourth-quarter earnings should be between $15 million and $20 million. A year earlier, earnings were $22.4 million. The S&L said annual earnings should be as high $124 million, more than three times the 1984 amount.