George,

At last I might be able to answer a question of yours instead of asking one... So yes, there is an electrical code, but as far as I know it's not european. All the Bosch components use it, but I wouldn't say it extrends to all european brands. Probably rthe german ones at least.

I found this link >http://engr.oregonstate.edu/~whitehbr/bmw/technical/bosch.html< for a list of some of these designation. When comparing with the numbers on my relays & amazon wiring diagram, I found it's quite accurate. This might be pretty useful to find alternative components to replace the ones on our cars. So far, I haven't been able to see if the "modern" relays (those housed in coloured plastic boxes) are still using this code. They should be, though, since it's a DIN norm.

Hoe that helps.
Séb