Hi Tas,
The plate was usually mounted on the face of the Laz platform. A lot of them have disappeared over the years. There are no other ID markings that I'm aware of on the boat. Too bad you didn't get any old sails with it.
I've sent your build number to a couple of places and have contacted some of the long-time R19 types around here who may be able to help. I also put a post into the Secretary of the R19 Class Org. He directed me to the Class Historian to check and see if they have records that go back that far. I'm awaiting a reply from him. I'll gather up the contact info and get it to you.