BSR without heat ring?

When I found this, I was a pretty confused. Too much build-up to see any markings, but obviously no heat ring, but the handle was a flattish BSR style. After seeing a similar skillet on this site ID'd as a BSR, I believe this is one too. I assume Red Mountain period - is there a way to determine early or late?

https://lh4.googleusercontent.com/-OS9vZqje0zY/UwtbBEc81fI/AAAAAAAABcc/gAu54RKVdiU/s128/photo.jpeg
https://lh4.googleusercontent.com/-WsirANxphAw/Uw9TPWE_MDI/AAAAAAAABfU/2j8A2k3cSuY/s512/photo.jpeg

We can typically consider smooth bottom skillets to be later in a manufacturer's production that those with heat rings. We also usually note that, if there is a difference observed, pans with smaller pour spouts indicate pieces that were produced as a manufacturer transitioned to automated processes, in order to reduce breakage from the relatively rough handling when pans were broken out of molds, tumbled, etc. This pan, if BSR, represents something of an oddity, in that is has the older style marking, the larger spouts, but the smooth bottom. Best guess, IMO, is that perhaps BSR toyed with the idea of producing a smooth bottom line at some point in the Red Mountain period, but decided not to continue further (with the exception of their deep skillet/chicken fryers).

That's interesting - thank you Doug. I love a good oddity.