Airtronics Championship Series
Rx's were not narrowbanded. It is the transmitter that required the narrowband check and even then some could not be approved, only the TX would have the gold sticker If not it is unlikely that radio is or has been legal since 1991.
In Most the single conversion Rx's could not be narrowbanded so the standard procedure was to have the Tx checked and stickered then a new narrow band Rx used.
John