Anyone who is really interested in buying Leica lenses, new or old, will probably have done enough research to know the speeds that correspond to the names.
Noctilux: f/1 or f/1.2 (so they'll say if its the rare f/1.2)
Summilux: f/1.4
Summicron: f/2
Summaron: A trick one at 28/5.6, 35/3.5 and 35/2.8, so they'll say for 35mm.
Elmar: This is another trick one at f/2.8 (50mm), f/3.5 (35mm, 50mm and 65mm), f/4 (90mm and 135mm) and f/6.3 (105mm) so they'll say for 50mm.
Summarit: Another trick one. Formerly (over 50 years ago) 50/1.5; modern versions all f/2.5 (35-50-75-90)
Elmarit: f/2.8
There are various older lenses that also correspond to a given aperture at a given focal length: Hektor (28/6.3, 50/2.5, 73/1.9, 125/2.5, 135/4.5) Thambar (90/2.2), Summar (50/2), Summarex (85/1.5), Xenon (50/1.5), Summitar (50/2).
But as cries of 'elitism' go, this one seems pretty feeble to me. If you don't know the difference between a Summar, Summitar and Summicron, perhaps it would not be a very good idea to buy any of them until you have a better idea of what you're buying.
Cheers,
Roger