I think it is a 50 1/2 to 52, Willys went to the 3 bar grille for the 53 model year. That said it looks pretty good aside from some surface rust on the bar. Would fit up to 56 with no problem and would work on 57 to 64 if you don't use the fresh air heater.
My 53 has a 3 bar grill, so at least some of the 53s got it. It's possible some 53s didn't get the 3 bar grill because Willys was still using leftovers from previous years, as per their MO.I think the 3 bar grille came out in 54. Anyway, it looks like it came off of 6 cyl. The shroud isn't long enough for 4cyl. That would be 148 or a 161.