Originally Posted by
P!N20
I'm not a 3Rensho expert, but the serial number placement and format doesn't correspond to other examples:
Google tells me the A prefix denoted frames exported to the US, where a C prefix is for the domestic product.
The serial number is for a custom order or prototype bike. These are fairly common here in Japan, I've had a couple from other makers. I'll take it down to the Blue Lug at Yoyogi Park, the paint guy there is pretty knowledgable about these bikes.