N15CS or G15CS

Hello
I have a what I thought was a Norton N15CS. The engine number is N15CS/124034 but the gearbox number is MA19165G. Far as I can tell MA is intended for Matchless (G15CS) the N on engine is a bit messy looks like could have been stamped over a G. Any idea what the hell the bike is?
cheers

Depending on the orders received, the AMC factory in Plumstead, London happily remodelled hybrids. I have come across an instance where a G15CSR was revamped into a N15CS, but I've never heard of a G15CS being remodelled into a N15CS. There is no sense in doing so, as the two models were identical, apart from paint schemes, transfers and tank badges. Next question, does engine number match the frame number (124034, found left downward of the headstock). If numbers match, someone at the factory made an error during punching, some metal would have to be ground off, and an N to be punched overlay style. It's not an uncommon observation.
To be sure of the bike's true identity, I suggest you order a factory record transcript or a quick check of the records.

Please note the picture showing location of the frame number on duplex frames does not apply to the hybrids, such as your bike.

- Knut

Having recently assisted on a N15CS I noted that it had the Matchless style gearbox casting as apposed to the Norton type but I cannot rember what prefix was stamped on the casting.

All genuine N15CS bikes should have an "NA" stamped transmission, as did 650/750 Norton Domi models made 1963-68. The suffix letter varied.
As far as I can tell, the Matchless-styled gearboxes had a 5-digit serial number, while the Norton Domi-styled gearboxes had 4-digit serial numbers. AMC produced more Matchless heavyweight bikes than corresponding Norton bikes, which may explain the choice of series. That is, until the Commando model apperared. In addition, there are visual differences between the gearbox shells.

- Knut

Thanks , I'll get factory record check.