The vault at Monumental Life Insurance Co. at Charles and Chase streets is one of many antiques in the building. It was built in 1939 for $50,000 and held all the company's assets until 1990, says treasurer Walter Weiss. "The doorwill not close if there is asmuch as a pin on the floor," Weiss says. "It fits like a glove." The company opened its building to the public earlier this month as part of a yearlong celebration to mark its 150th anniversary.