Avro 504R Gosport

The Avro 504R was a mixed modification in order to update the original 504K. It featured the same skid as the 504K, but had the engine and wings of the 504N. It was presented to the RAF but it wasn't found suitable for the training role due to the low reliability rates.

It was sold to Argentina, where it was locally produced by the Fabrica Militar de Aviones (Military Airplane Factory), Estonia, where it served until 1940 and the Peruvian Air Force, where also some ex-Argentinean made machines ended-up.

Sources:
1. http://www.airwar.ru/enc/other1/avro504r.html (translated)
2. Salamander Books - The Complete Book of Fighters
3. https://en.wikipedia.org/wiki/Avro_504