I joined 737 NAS in January 1967, we had Wessex HAS 1’s and the Sonar 195 development Wessex XM328, later we started to get HAS 3’s . I don’t have a photo of the inside of a HAS 1 but compared to the HAS 3 it was very basic . No Radar, basic autopilot and Sonar 194. The Sonar had a 90 foot cable [ 195 had 300 feet ] with a ball transducer with 4 wooden stabilising paddles. The displays were a bearing indicator and a range display of the ‘wet paper’ and moving stylus , just like one would see in black and white WW2 movies [ not the same, but almost, http://jproc.ca/sari/asd_et2.html ]. The main AS detection was by the operators ears!, the operators all being ‘old & bold’ AS sonar operators transferred from RN General Service [ships]. The operator sat left, as where the radar operator does in the HAS 3.
The HAS 1 equipment certainly wasn’t secret, the HAS 3 was, at the time ~ although the spy ring at AUWE Portland ensured the Russians knew everything.

Long time ago, my memory may lack on the detail side.