That's correct. Most vintage drums have a rounded bearing edge profile.
As the story I was told goes: The bearing edges were rounded to help prevent the (at the time) calfskin heads from tearing along the perimeter. This allowed them to be tensioned higher without ripping the head.
And when synthetic heads came into being in the 1950's, no one bothered to change the edge profile -except, I guess, Rogers (Although my mid-70's Rogers "Big R" shells have rounded edges -go figure!). Anyway, it went on that way for quite awhile. And then all of a sudden, drum R&D went crazy and, as a result, almost everyone started doing the double 45 degree bevels. This edge profile moved the contact point inward making the actual diameter of that point of the shell, smaller. Additionally, since mylar (plastic) was less prone to being "cut", a sharper double 45 edge allowed a wider tuning range, muted the head less. And that made the drums sustain longer (which was an impressive thing for all of us who go into a drum shop and tap on the floor toms with our finger in order to determine the quality of the sound! -heh heh).
But, then, it seems that people grew tired of that "ultimate" sound ;) and started going back to the warmer vintage sound of the rounded and more shallow edge, again. And here we are!Burger Kin