Here are some photos taken from an auction for a pair of what are described as a pair (100mm, 120mm) of NOS hubs. (I don’t intend to bid on or buy this rather swish pair; this auction is just an illustration.)
Are they for single speed or instead for a set of five sprockets, and how does one learn this from the photos? (Yes, you guess correctly: I don’t know jack about this kind of thing.)
Sheldon Brown’s “Tool tips: Hub overhaul” (on cup-and-cone hubs) makes me nervous. It’s been decades since the last time I saw ball bearings that I’d extracted from some part of my bike: I never managed to get them back in again, and even if I’d succeeded I’m sure that the result would have had more friction than there’d been in the first place. Hoping that the better bike shops still offer this service … or perhaps I should buy a really cheap pair of old hubs just in order to practise on them.