It's said that early 1.4/50 are inferior to the 1.8/50 but this might only be hearsay. Seems to be that the same lens designs were used over more than two decades with varying quality standards and different kinds of coatings. The 1.8/50 inscribed "made in japan" on the frontring have an excellent reputation though. I have both, an older 1.4/50 and a mij and can't tell the difference.

Ulrich