On my boat the hull number, i.e. the serial number given it by Tylers, who moulded it, is on a label fixed inside the transom. You have to peer inside the stern locker with a torch to see it.
Our 1989 boat has the HIN moulded into the gelcoat on the starboard quarter of the transom. It's back to front as in a mirror, but you don't need to be a Leonardo da Vinci to decode it!
My application disapeared for 3 weeks then I got a letter asking for the HIN or for a statement that the boat was built pre 95. I thought I had put the build year on the apllication ( 1975) but have responded and await a reply.
So I would put 'pre 95' on anyway ( if it is of course!!) just to save more paperwork.