Crankcase number help

[jkardine]

Hi folks, just a quick question to see if someone could help with some identifying numbers if that's ok.
Recently bought new crankcases for my A10 with case numbers [matching] CA10 RR 4***9 with HCC stamped on there too.  We've dated it to about '57 but a bit baffled about the RR bit as I thought it was just R for Road Rocket and HC for high compression.
Could anyone shed some light on the issue please?
Any information would be greatly appreciated
Dan

[JulianS]

Some Road Rocket were stamped CA10RR.

The number 4***9 is too long, would be 4 figures if starting with a 4.

The very first export only Super Rockets (the modified head) were numbered  4501-5000.

[jkardine]

Hi Julian,
Thank you for that info, to be honest the last digit does look different from the previous 4, and Im lead to believe the company I bought it from imports from the US, so that would clear up one problem, now concerned if I can actually use it if another number has been stamped. They said the crankcase is genuine and if Im going to send DVLA an updated V5c whether this would be acceptable.
Many thanks for your help, its appreciated.
Regards

Dan