How many 50s do we need: 50mm f/1.8 AI-S "long nose"

The 50mm was the "standard" kit lens in the 1970s and there were a number of iterations across the AI and AI-S variations from the 1980s, ultimately leading up to the plastic 50mm f/1.8D. With so many iterations available of the f/1.8 AI-S, what are the key differences when looking to pick one up, especially the earlier AI-S "long nose"


^{Nikkors f/1.8D | f/1.8 AI-S "long nose" | f/1.4 AI-S}