From a little research, I have found dozens of anomalies. But! I believe these Brisfits belonged to 5 Sqn who were patrolling the North-West Frontier of India from Apr 1920 into WWII. 20 Sqn appeared to have applied their codes on the Fin.

J6598 (C) apparently served with 5 Sqn in Jan 1924 according to Air Britian ‘J’ Files.

The ground equipment in the first photo would have yer elf & safety guys havin kittens. 2 x oil drums for steps. Excellent!:D:D