This is kind of cool, seems they were only made for about 2 years, maybe a couple months more.
This is a "number 8" size pan of the "Century" series, with a diameter of 10 5/8 inches. It's slightly larger than the "number 8" sized pans from other manufacturers, such as Lodge or Griswold. Be sure to note the following:
BS&R was the only manufacturer to use the abbreviation of NO. for "number," and IN. for "inches."
The lack of a MADE IN USA mark indicates this pan was manufactured before the year 1968. This dates it to anywhere between 1966 and 1967 (or early 1968 at the latest).
A rounded font style of the lettering, as opposed to the block style and typewriter-style fonts used by other manufacturers. The font size is smaller than the lettering used in the older Red Mountain series.
As with the older pans, there is a thick and prominent heat ring – the circular ridge – on the bottom of the pan. Other than on their skillets, the heat ring was removed from the bottom of some BS&R "Century" pans; in particular, BS&R dutch ovens from this period. They were still stamped with a NO. and measurement.
The teardrop-shaped scoop on the underside of the handle, unique to BS&R pans.
Credit for this goes to Modemac's wiki BSR page
