The biplanes in post #371 are Avro 626s. They are not the same as the Avro Prefect, which the 626 is frequently and mistakenly called. The 626 was a different aircraft and was designed as a three seat gunnery trainer, whereas the Prefect had only two seats. Even the Avro Putnam book gets identifying which is which wrong. The rear gun position on these Austrian aircraft can just be made out behind the rear forward facing cockpit and was blanked over.