On Mar 27, 2001, Robin Barker on the MGA Twin Cam Enthusiasts Group wrote:
"The production records at Gaydon, UK include all of the accessories fitted to a particular car. They also include a 5 or 6 digit number. I am not sure what function this number served. All home market cars were Y followed by 4 numbers, most but not all of the other cars were 5 numbers. I speculate that this number was a work order, production control or inspection record ID# which was unique to each car. Production / inspection records were possibly filed away by these numbers and included records from the body shop, engine works and MG assembly line, each created as the car and it's components were built. As well there would be info on what dealer / distributor ordered the car as well as accessories and specials fitted. The archivists at Gaydon do not have any records which link with these numbers so I further speculate that if they ever existed, they have now been resident in a Berkshire landfill for the past 30 years or helped fire the records office boiler on a cold winter's day a long time ago. I only mention this as you never know what members of our group know or have squirreled away. A fairly complete set of records for the prewar MGs exist so we can only hope to be so lucky".