The CZ-prefix of the S/N may just be a coincidence. Prior to 1989, the first alpha character in the Csepel format indicated the frame style, with C designating a city bicycle with a 24" or 26" wheel. The 2nd alpha character was the year indicator, with Z designating 1986. So, this should be a 1986 model or a 1987 model manufactured in late 1986. Given the similarity to the 1988 model, I'm leaning towards the latter. Are their extant 1987 Schwinn ATB/City catalogues to confirm?