The Nimbus I owned had a varnished panel about 400 x 200 mm in the middle of the aft bulkhead, a screw fitting and the name Nimbus painted on it. I'll have a photograph of it (the aft end of the cockpit) somewhere and I'll see if I can find it if it is of any use. We bought Nimbus from a member of the Aurora Yacht Club (Nelson) and used to sail on the madflats behind Mapua. In winter we sometimes took the outgoing tide and stayed out at sea for the day, returning on the incoming tide. The only requirement by our parents was that we be home in time for dinner. A couple of young teenagers, no VHF, no cell phones, no comms of any kind. That's how you learned risk management though we called it "What if the mast fell down?". If we'd drowned ourselves we'd never have been allow to go sailing again - so we didn't drown ourselves.
Sandy