TOPIC: Where can I find a boat ID number?

I'm looking at a Herter, I think its a 15.5 ft St Lawrence, and can't find its boat mfgr identification number. Where would it be? I think its a 1960s boat. Open boat, no fins, no windshield or dash /wheel. Also looking for advice re:what to look for, any problems common to these boats. I know this is a lot to ask, I'm a newbie that started late:-)

It doesn't have a Hull Identification Number. They weren't required until 1972. Many manufacturers put some sort of serial number on what used to be called a builders plate (usually a Boating Industry Association label) but not all. If there's no label then it probably doesn't have a serial number.