MK IV DHC - nummer on chassis

Hi all,
My MK IV DHC has a number stamped on the back transversal of my chassis, have no idea what the meaning is of this number as my chassis number is 637212 and body number C1267. Does anyone know the meaning of this number?

Well, if nobody has a better guess, I’ll offer mine.
These chassis frames were made by Rubery Owen for Jaguar. I suspect that may be an inventory or production number used at Rubery Owen for billing Jaguar.
I looked up the total number of Mark IV 2.5s and 3.5s made post-war and it was 6281 cars. The 1.5s were a different shorter chassis and there were 5761 cars. If Rubery Owen stamped them all in a single sequence it might make sense that way. Or they could have carried on the 2.5/3.5 sequence from the 1940 production run.