It's the f/1.4 lens; if you look carefully, you can read "1:1.4" on the front rim.
The smooth-looking part is the lens hood; looks like a Kodak or Tiffen series size item, which would have been deeper than the Canon S-50 hood and would have allowed the use of series-size filters, which were popular in the late '50s and early '60s.
(For those not in the know, series filters -- so-called because their diameter was designated "Series V", "Series VI," etc. -- had no threads; they came in smooth metal mounts. To attach them to a lens, you'd attach a clamp-on or screw-in series filter adapter to the lens, drop in one or more filters, then screw a retaining ring or lens hood into the adapter to secure the filters in place. It allowed the use of the same set of filters on various lenses, encouraged the photographer to use a lens hood, and removed the risk of cross-threaded or jammed filters. Like the sturdy, positive ASA flash contact, this was one of those cases in which the American manufacturers had a better idea than their European and Japanese counterparts, but couldn't make it stick.)