I knew Paramount and their cords, but somehow never saw this page.
That ASA thing also explains why I never came across it, whereas a fellow US-member told me it would be common.
Strange enough though I have not found that socket in my US strobes-literature of the 40's.
I once restored an old folder that came with a small folding flash bulb refelctor that had a rigid connector so the unit would sit right on the shutter itself. If I find it in my collection I'll send up a pic of it.