Any version of the 50mm/1.8 (aside from the Series E)
There's nothing wrong with the Series E. However due to its simpler coatings and its small size a hood is a must.
I've read of an AIS version of this lens that looks like the Series E and doesn't have the rabbit ears, but I've never seen one.
There are 3 versions of the 50mm /1.8 AIS:
1- Long nose. It is almost identical externally from the AI version. The only give away without looking at the mount is the double row of 22 in orange.
2- Pancake style based on the Series E and only sold in Japan. I have one of these. It focuses down to 0.45m as opposed to 0.60 on the Series E. It has also the aluminium aperture ring and a nice rubber ring for focusing. It is heavier than a Series E. IT was the standard lens for the Nikon EM in Japan and it is the one that appears in the Japanese brochure.
You can see this version here:
[video=youtube;LlYxSJQyKcE]https://www.youtube.com/watch?v=LlYxSJQyKcE[/video]
3- Pancake type very similar to the Series E MkII. It also focuses to 0.60m and has the same aperture ring. Focusing ring is in plastic.
There is also an AI version of the 50mm/2.0, but it'll be harder to find.
A very nice lens it is. Some say the earlier Nikkor-H.C is slightly better. Personally I haven't seen any difference.
It was dropped from production in or around 1979/80.
The prospect for the EM dated from 79 still lists it.
It was sold mainly with the EL2 and the Nikkormat FT3.