Quick aside --- With the similarities in construction, I have wondered if Gruen licensed the Pioneer patent for all of its threaded import cases from the period. It is possible, since the patent was filed in 1939, that the technology had been available.

T Haven't found a clearer image...

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent, is:
1. A watchcase comprising a movement ring, a bezel having a bore adapted to receive said movement ring in close engagement, an annular recess in the upper peripheral portion of said ring, an annular recess in the lower peripheral portion of said ring, a back provided with a recess complementary to said last recess and having an outer wall portion in the form of a flange closely engaging the periphery of said movement ring, and a gasket seated in each of the recesses of said ring, a crystal having peripheral portions extending between the bezel and the upper gasket, and means for drawing said bezel and said back together, whereby said gaskets will be compressed and will effect a watertight joint between said ring on the one hand, and the crystal, the bezel and the back on the other hand.

2. In combination in a watchcase, a movement ring, a bezel having a bore to receive said movement ring in relatively close engagement, a recess running around the upper peripheral portion of said ring, a compressible gasket seated in said ring, a crystal having peripheral portions extending between the bezel and the gasket, and means for drawing said bezel against said crystal, whereby said crystal will press against said gasket and will compress it axially and expand it radially so as to cause its peripheral portions to press against the wall of the bore in said bezel, and to effect a Watertight joint between said ring on the one hand and said crystal and said bezel on the other hand.

3. In combination in a watchcase, a circularly contoured movement ring, a back having a peripheral Wall of an inner diameter to receive a portion of the movement ring, an annular recess in the end of said movement ring, a compressible gasket seated in said recess, said gasket being of a diameter to engage the inner surface of said peripheral wall of the back, and means to press said back against said gasket, whereby said gasket will be axially compressed and its peripheral portions will expand radially and press against the inner surface of said peripheral wall so as to make a watertight joint.

I likely could email Charlie Cleeves and ask for a close up of the ad. I'll update if I hear back.