What does the antenna look like? Try to identify it with some of the ham catalogs that we all get in the mail after licensing. Have someone at your local ham club check it with a UHF/VHF meter, prior to use. You are smart not
to transmit on it before you have it checked out.
However, if he had a dual band radio, I am betting that it is a dual band antenna.
You would probably get better response if you posted this in the "Mobile Ham