I have a 50/1.8 Mk 1 with a date code UB0200, so that's February of 1987. Pristine condition.
It's for sale if anyone is interested.
+1 Mine is also UB0200. It looks even more pristine, if that's possible, than yours.
5D IV, 5DS R, 7D II, EOS-M, Powershot G3 X, 400mm DO II, 300/2.8 II, 1.4xTC III, 2xTC III, EF 1.8 STM, EF 70-200/4 IS, EF 24-105, 15-85, 100-400 II, Sigma 10-20, Sigma 150-600mm C, EOS-M5 15-45, f/2 22, 11-22, Samyang 8mm f/2.8 fisheye