Actually, this does not match the serial number format. The format for 1980-1986 consists of two letters followed by 5 numbers. You are missing the 2nd letter (month indicator) and have 2 extra numbers. Yours is the 1st post 1986 serial number that has been submitted, so there is the remote possibibility that the format may have changed again. Could you please doublecheck the serial number? Thxs.
The fact that the tubing label states Ishiwata does place it very late 1980s, but I do have the 1988 specs and while they state Si325 tubing, the components are SunTour Ole, derailleurs, Sugino crankset and Dia-Compe- BRS200. If the components are 1988, the bicycle itself may be a 1989 model.