Air filter housing blue paint and number

[Stevejaguar]

Series 1 2+2
Whilst stripping layers of paint from the air filter housing and the triangular air intake box I have come across a layer of blue paint below many layers of silver paint. There doesn't seem to be any paint below the blue. Was this the original undercoat, or has some previous owner completely stripped it and painted it blue, presumably to match the original colour of my car?
Also, there is a number, 72102 L9, about 3mm high, stamped into the air filter housing. Any ideas what this could be? It doesn't match any part number that I can find.
Steve

[Philk]

The air filter circular canister was black on all 3.8 E-types and early 4.2 E-Types prior to switching to silver (in line with the triangular delivery enclosure that sits on top of the canister). The latter was always silver in colour (with a slightly hammered texture). I can only presume that, in line with your thinking, someone once coloured these to match the car (was blue its original colour or was it resprayed to that colour at some point?)

[Stevejaguar]

Thanks Philk.
That was my thinking and yes the car was originally blue. It did have a respray in its original Blue sometime before 1978 after a bump. In 1988 it was resprayed red.
Steve

[dlgis]

I reckon blue was once a very trendy colour choice for air filter boxes. Here’s my car in its formative years sporting fetching blue items. The original colour of the car was ODB.

[Stevejaguar]

Darryl, how odd. Looks the same shade of blue as mine was.
Steve