Is anybody familiar with the SONY E10W from about 1984? It is slightly smaller than the SRF-59, is speakerless, and is mono (and as result, came with a nice earpiece for one ear. It has an analog dial on the top of the set as opposed to the front; the top of the set is metal, the rest of the case is plastic. It has a push button to turn it on, another to turn it off. The set automatically turns off if the ear piece is taken out, and turns itself off as well after about an hour to save batteries.
It is slightly more sensitive and easily more selective than the SRF-59 when the bottom right of the set is held by a finger (thumb works well). When a finger is not placed in that location, the set is less sensitive on the upper frequencies (say, 1100 KHz and especially above). The nulling is exceptional, even (amazingly) clearly better than the 59.
The tuning is stiffer than the 59, and, with the control on the top edge, more difficult than the 59.
I wonder what kind of a chip SONY used in this set. I also wonder how SONY managed to make the 59 equally sensitive across the dial without the aid of a well placed finger!