WAL preamplifiers were listed in Hi Fi Year Book 1967-68, then under Elstone Electronics.
These were battery-operated units for matching tape, microphone, or pickup inputs. That suggests that they were intended for use with amplifiers or control units that did not have low-level inputs, not too uncommon at the time. And there were other makers of this kind of preamplifier for domestic use.
Evidently WAL moved on to mains powered units of the same basic type. I imagine that the three-way selector was less intended for daily use than to preset the unit for specific applications. Magnetic cartridge matching and equalization may have bene the main objective, but as the same basic circuit could easily be configured for use as microphone or tape head preamplifier, it would have been easy enough to include those facilities.
Re Sugden’s involvement, the disc preamplifier section of its C51 control unit, although mostly intended to do the RIAA job, was configurable for microphone, and tape head inputs, as well as for different disc equalization curves. I think that there was also a plug-in for the A.R. Sugden ceramic cartridge, which was something of a maverick amongst higher quality ceramics in terms of its characteristics and required loading (it was outside of the range of the Burrows parameters.)
So perhaps the design of the subject WAL unit drew from that of the Sugden C51.
Cheers,