My thanks to the eagle-eyed G1MRA membership secretary, who informed us shortly after the listing was published that this was produced by Cheddar.
Update 29/9/26 - further thanks to reader Peter Thompson, who has identified this as a Cheddar "Riesa".
A 45mm narrow gauge gas-fired 0-4-0T, with strong Orenstein & Koppel flavour.
A very well put-together locomotive, unusually it's entirely remote controlled with no allowance for manual control. The two servos are mounted underneath the cab floor, with the regulator valve mounted just above the front axle and piped into the steam dome.
In good order throughout, we've replaced the water gauge seals and stripped out the antique Futaba FP-R115F analogue receiver, replacing it with a modern Planet 2+2 2.4ghz receiver and matching transmitter.
We've undertaken hydraulic and steam tests - it makes steam well, the safety valve blowing off at 40psi, though with a slight leak on the regulator. The boiler showed no signs of leaks at twice working pressure; without stripping the cladding we've declined to issue certification, but would warranty as sound.
Complete with new Planet transmitter.