I had briefly looked at Fiedler Gothic before, but only at the “5” weight, and ruled it out because of the smaller apertures in S. But a) this detail might be different in a bolder weight (and this appears to be a bolder one), and b) it’s something that could be easily modified. So, yes, Fiedler Gothic looks like a likely candidate. It was around in 1965, too.
Below is an overview over the caps in four of Fiedler Gothic’s weights, from PLINC’s 1971 catalog.