Another data point: WK4000xxx, mink and blue, has the C C cutouts, fastback stays, Cinelli style fork crown, fork chromed approx 2/3, stays roughly half chromed, no eyelets. Hopefully this is a '74 because I can't vouch for the parts being on the bike from new. BTW: I thought the letters indicate which fortnight the frame was constructed, rather than the month.
Pete Geurds
Douglassville, PA