Guilloche on Brass Deco Easel-Frame, Mostly Intact

It's 2 15/16" by 2 7/16", with a 1 5/8" diameter window; weight is ~2 1/4 oz. It is missing its back-piece, which would secure an image an' stiffening panel, cam-locking into place. The window is modern, float-glass; it looks to be a repurposed flashlight lens.
This was my first exposure to guilloche, probably in the mid-60's.
I recall being as fascinated by the carefully done corner details, in white rather than pale yellow surrounding them, as by the guilloche itself. The grecian-key border was, as now, heavily tarnished. Also highly attractive was/is the cobalt border. Y'all would thing by now I'd have found a wee pic of a sweetheart or grandchild to populate it...but I confess to have buried it, an' until recently ignored & forgotten it. I resolve to do better, an' soon! There's nary a mark on it; perhaps the missing part was marked. Can anyone offer a probable maker, an' possibly an era of origin? Thanks for lookin'!

 

Clock case

 

Sure! Of course, Brad...Thanks!
So it isn't missing anything, not even a 'window'...a clock has its own crystal.

 

Thats a beautiful frame nonetheless. Id have bought it !

 

Two clock cases in my house are frames!

 

All three pieces are beauties and make great frames.

 

Excellent use of them. Very nice