Strange sticker/part number

While pressure washing my 1983 110 I noticed this sticker appear from under the grime.

It's located on the upper left region of the bulkhead next the brake servo.

Any ideas what it means?

MRC 8308

E11 15R 03713

The only thing google throws up is an American with the same sticker on their early 90 who also has no idea what it means.

I've spotted similar sticker on ebay "MTC7503", but it's a different part number

E11 means that the part is approved for use on U.K. roads by the EU. Normally see them on windscreens and glass.
... me thinks!

Colour code????

Not sure colour code would need EU type approval?

If it's an EU approval sticker I wonder if it has something to do with the braking system?

EDIT:

I have been doing some research and E11 is the Member state Authority who approved the part. E11 is the UK.

EDIT 2:

It seems that all vehicles sold within the European Union must be type approved and i'm starting to suspect this the the EU type approval number for either the engine or the vehicle.