Anyone recognise this classic frame number format

[marvin71]

Hello, I have had no luck with identifying my 1970/80 mixte twin lateral frame with Haden lugs. Details of lugs etc are shown on an earlier post.

This is the frame number on the bottom bracket lug. Does anyone recognise this format please. I am trying to identify the frame builder.

Many thanks

Marvin

 

[Midlife]

Sort of looks like a telephone number?

C21 is Shrewsbury

Shaun