4572483 and 4614685900 stamped on.
Any thoughts on flow rate Arno ?
Looks like it's all basically the same airbox model. Probably small production variations over the years giving slightly different (updated) part numbers. The housing looks like it has a resonance chamber on it as well to cut more intake frequencies/noise, so the different models likely had some 'tweaks' over time in areas like this. All seem to use the same filter element.
Plenty available across the EU 
http://www.autoparts...9/air-filter/1/
Looks like a very nice option for these cars. Much nicer access to change the filter element, even compared to the OEM box.
The 'cyclone' style side air inlet setup does mean it may at peak flow a little less than a plain filter box, but the advantage is that the filter element loads up with dirt a lot less quickly as it gets flung to the outside of the box more and will drop down/out when the engine is at low rpm. Quite common feature on truck and agricultural machines. (some even have active suction to remove larger sand/dirt from the housing)
Max/ultimate flow rate in m3/minute (usually at max 10mbar pressure drop or so..) will depend a lot on the airbox design and often less on the actual filter element. If this filter element were to be fitted to an un-enclosed mount it would probably flow quite an ridiculous amount of air. The peak flow usually gets restricted/slowed by the twists and turns the air has to take in the housing and only after the filter loads up with dirt can/will it become the bottleneck.
An 'open' paper air filter is not so useful outside stationary/enclosed applications like generators and such though
Bye, Arno.
