The Courtenay model 38 used a diamond-shaped point of light to indicate the frequency, in a system they called "Phantom Ace" tuning. The 2 known cabinet designs were called the Opera (Tombstone model) and Ballad (Console).
The diamond shaped point of light is generated by two aluminium discs with opposing spiral-shaped slots cut in them. They rotate independently of each other and in sync with the tuning gang in order to produce a hole where the two spirals meet that indicates the position of the tuning gang.
I.F. Frequency: 456kc/s
Chassis Notes: 3-band chassis covering broadcast 550 - 1500kHz, Intermediate SW 2.1 - 6MHz and SW 6 - 18MHz. The chassis uses a unique spiral dial tuning system with an effective tuning distance of over 2 feet and fast / slow tuning to provide very good control of the frequency. The spiral tuning system is complex though, and unless its been restored it always seems to be broken on sets found today. The dial assembly consists of either a red-tinted spiral line of light or a red dot (depending on brand) that indicates the frequency on a novel trio of spirals for the three bands. The band selector slightly rotates the system so that the dot or the end of the line aligns with the correct band. Setting this up takes some patience and trial-error (There is some indication that there was to be a service bulletin from RCNZ for the dial assy, but it has never been sighted).