Bosch Spark plug codes

The following codes of Bosch Sparkplugs I found on the internet:
    R   : Resistor plug
    C   : Copper Core
    P   : Platinum Core
    T   : Triple tip
    W   : 14mm Threads
    D   : 3/4" Thread reach with extended tip
    P-4 : Platinum 4 tip
The BMW Twin uses Bosch W6DC spark plugs what means they have 14mm Threads, the temperature range has code 6, 3/4" Thread length and a copper core.

(c) W.P.Barendsen 2001