Gee Gerd, I really can't find out anything about the beach buggy except for an eBay ad, which gives very little information except that it is GRP, and fits a VW. I know a bit more about the yacht, beside the posted ad, but not much. The yacht is steel, and built by DEVO in Hellevoetsluis.
My connection of both being made in The Netherlands was only speculation, but, if this is correct, I will go a bit further and speculate that perhaps the beach buggy was also a product of DEVO, since boat builders are frequently experts in GRP construction.
While we are on the subject of connection, can you relate the connection of H (Fiat SPA TL37) and 23 (M-B 300 SEL AMG)? I had identified both vehicles, but couldn't come up with a plausible connection.