Federal Bureau of Investigation agents and state and local police are still searching for the two master holdup artists who knocked over the Harvard Trust Company Monday.

Posing as guards from Armored Banking Services, Inc., the pair walked off with a $165,000 Polaroid Corporation payroll.

One of the men was dressed in the firm's uniform and signed for the cash with a signature that also appeared on the master list the trust company uses to check the authenticity of its money carriers.

The pair peacefully pulled off the biggest haul in the Harvard Trust's history with the help of "inside information," Cambridge Police Detective William Durette said yesterday.

The men knew the day and hour of the payroll pickup and the exact amount to be distributed, Durette said. They were "obviously professionals," he added.

Cool Hand Luke

The thieves were attentive to minute details. Apparently to avoid recognition, they gave the name of a messenger who had never made the main banking office run before. The man who signed for the money explained away any discrepancy between his signature and the authorized signature by complaining that his hands were cold.

Police have reconstructed sketches of the two men, and released the drawings to all Boston newspapers and television stations. Intensive investigations are being conducted around Harvard Square to locate bystanders who might have seen the pair leaving the bank after the job.