Do I have a browning challenger 1 or 2 serial 70343 U74 purchased 38 years ago new?

The U74 suffix to your serial number indicates that your Browning challenger was made in the year 1974.This also revels that you have a Challenger I because the Browning challenger II was not made until 1975.You should have Plastic wraparound grips which were only made on the challenger I in 1974.The challenger I was produced from 1962-1974.The challenger II was made from 1975-1982.I hope this helps?