unknown gramophone pickup Circa around 1928-32?

[herrickpickups]

wondered if anyone knows who built this one please ? from the build construction / quality & fixing screws that are all metric threads I'd say it was German or at least European but the front plate is missing which would have likely had a logo on it. There is an Identical one of Norman Field's website but I cannot find anything else. Possible makers- Efesca, Hegra, Blaupunkt/ Blue-spot, Vesshof, Phillips & Loewe ?