The earliest found example (as known to me) of Rowe Industries’ first attachable pickup for archtop F-hole instruments appeared in their green fold-in sales leaflet Form D100, dated November 15, 1941. Just four items were shown – the models FH and FHC for F-hole guitars and the RH and RHC for flat-top roundhole guitars.
This shows the unit as installed. Note the edgewise volume controller, the four flush slot-head fixing screws, the tapered shape of the assembly and lastly, the text – DeArmond – in Harry DeArmond’s own handwriting.