AW Whitley MK.III

Hi all I’m building a model of K8985 DY-J of 102 Sqd forced down in (then) neutral Belgium on 08/09/1939. On looking at the available MK.III photos I see some had the later Bomb aimers window as on the MK.V. Anyone here have a theory as to whether this was a retro fit on the OTU aircraft or were some of the operational aircraft including K8985 so fitted? The only picture I know of 8985 is from the rear starboard quarter.

Thanks in advance

Nick