how to identify alloys

[goffboy]

hey folks,

been trying to work out for the last while what alloys are on my TDi. they're 17", 15 spoke and i think they're off an R32 - can't be certain. all i know is their not original spec. had one of the wheels off the other day and on back it was stamped VW & BBS (on separate spokes), plus a host of other number codes, about six in total. which one is used to identify them? ET57? RT197?

any help gratefully appreciated.

ta,

E