rhm, the double cable stops are on the downtube, it looks like only single cable stops behind the bottom bracket. I believe some Osgears had a tension release cable for the front arm and the cable stop setup on the OP's frame would fit this arrangement.
I also think MauriceMoss may be spot-on with Ephgrave.
I saw your suggestion of the Osgear and have to admit, with apologies, that I didn't think about it seriously. I'm not familiar with all the Osgear variants.
The frame is a bit more like an archaeological site than usual. These cable stops and guides are probably original. The shifter bosses, whatever they are, are probably not original. I'd like to look over every inch of the frame and see I'd there are more signs of changes made.
Returning to the Osgear, I guess this would be the Cyclo Ace or the like? I can't find complete photos of that system. Was it sometimes mounted on a brazed on tab? What shifter(s)?