The Ultimate RCP was manufactured by Radio (1936) Ltd in 1955, production ran for 4 years.

Plastic cabinet model known as the Cygnet, and is both fairly common as well as a great performer for its size, helped in part due to its ferrite antenna.

Note: there is an earlier model (the RBZ) using this cabinet although the circuitry is quite different.

Another cabinet exists in mahogany veneer, as seen - the "New Sorrento" model using the RCP chassis.

Valves (5):
EARLY: ECH21, EF22, EAF42, EBL21, 6X4
USUAL: ECH42, EF41, EBC41, EL41, 6X4
LAST: ECH81, EF89, EBC81, EL84, 6X4

Chassis Notes (most schematics can be clicked to download a full size version): Note three different possible valve lineups depending on where in production the model came from.

General Construction Notes for Radio (1936) Ltd: Early Radio Ltd. schematics did not show the models, just the year, valves and bands, so some sleuthing is required to find the right one.

Early 30's Ultimate models with three digit model numbers indicated both the number of valves in the set, and the price it retailed for - for example, the model 856 was an 8-valve radio which retailed for $56 pounds. The equivalent Courier models were reversed, so an Ultimate 856 was a Courier 568 (theoretically, at least). This was the Auckland price though, and often the sets would retail for 1 or 2 pounds more in other centres, presumably to cover the freight cost of moving them around the country from the Auckland factory.

Note the use of old resistance terminology on older schematics: ω means ohms and Ω means megohms.

Some 1936-onward 3-letter chassis codes vary the last letter between brands, for example:
BBU - Ultimate model BB
BBR - Rolls (and Golden Knight) model BB
BBC - Courier model BB
All use the same chassis.

Golden Knight, Courier and Rolls appear to use the same copper-painted chassis while Ultimate chassis' are painted silver