TOPIC: Lyncraft Seabreeze Boat numbering

I have a 1958 Lyncraft Seabreeze Contessa 1900 -one of the first one built. It's on here in other places...the plate on the transom has number 5181836 on it. Does anybody know what this might mean? I'm doing a total rehab on it (not really a "restoration") - will post pix as soon as I get further along...just got the transom back in. Making some BIG mistakes, but they are correctable.