By definition this is a difficult topic.
I start it as a 'depository' for links when you 'discover' an aircraft previously unknown to you and which might be unknown to the broader membership.
My starter is:-
http://en.wikipedia.org/wiki/Vickers_Vincent
which I discovered when following links for the B17 Fortress - it was the type that 223 squadron operated in 1937.
They replaced another unknown type:-
http://en.wikipedia.org/wiki/Fairey_Gordon which 223 squadron operated in 1936.
They were both biplanes:-
http://www.wwiivehicles.com/unitedki...vincent-01.jpg
http://www.raf.mod.uk/history_old/images/gordon.jpg