Series 1 Chassis Number Question

Sorry for the double post, I have mentioned this in my 'Whats The Value' thread....
The series 1 80 from 1950, Im about to purchase has 5 digits before the chassis number, these are stamped into the chassis and ID plate on the bulkhead.
Does anyone know what they are for??????

The numbers are 10049, followed by the normal R06******?

Doing as much digging to allow a better barter for the vehicle.

Cheers

lee

Numbers stamped before the chassis number stamping (on the chassis) are just for internal use when the thing was put together. They don't really mean anything to us now. Suspect someone has put a new chassis plate on it at some point and put ALL the numbers down, not just the R-number.