now let's open the envelope.
the 5 screws copy is original Nikkor 50/2 Ai (35xxxxx), every aspect meet the Ai design: milled metal rabbit ear, 5 screw, no milled slot as Ais
the 3 screws copy is original Nikkor 50/1.8 Ai (18xxxxx), typically that AiS nikkor lens had the 3 screws, but this Ai50/1.8 only had 3 screws(I don't know why), other aspect meet the Ai design
both of them are my favorite lenses, I got several various copies of 50/1.8 earlier, recently got the 50/2 by curiosity after I read 50/2 paper in Nikon's "the thousand and one nights".
when I compare fully open image quality of nikon's Ai50/1.8 vs AIS 50/1.4 & AFD 50/1.4, I think 50/1.8 is better @f1.8, any 50/1.8 is smaller and lighter. but 50/1.8 is not very good at corner when fully open, center is good.
now I can make a test of 50/1.8 and 50/2, who is better, I will post later