Univox was an import/distribution company.They didn't actually make anything. Univox guitars were made at the Matsumoko guitar in Japan,who made guitars sold under many brand names such as Aria, Westbury, Westone, Epiphone, and others. The Hi-Flier line was made from 1968-1978. As to the serial numbers, the Matsumoko factory burnt down in 1988 and there's no existing records or info on how to decipher their serial number system to establish what year a specific guitar was made. What's intersting about your guitar is I can't find another picture of a Hi-Flier bass with the same pickups as yours has. All the pictures I find on the net,including catalog pictures, either show the early version with the black plastic covered single coils like this:
Or the later version with humbuckers like this: