I can't seem to find a thread for this, the new seach machine really isn't working for me.
Anyway i have a OC-2 with serial number ZA23631 MIT which suggests it was made in May 1989 it has a type 3 serial. the decoder says that type 4 was from March 1989. so, either the data is slightly off or my pedal is a strange one. just letting you guys know.
Actually, what you have there is a type 4 serial number. Type 4 has 2 letters and 5 digits while type 3 has 1 letter and 6 digits. Did you perhaps confuse the types with the type of sticker? For pedals made 1989, this serial number may be printed on a sticker inside the battery compartment just like type 2 and type 3 serial numbers.