you can see the transition between these Mk III's and the early Mk IV's, I have a Mk IV with the red/pinky rubber under the stokingette covering, has the Mk III type eye pieces painted green which differ from the later aluminium easily removable ones, and an early Mk "II" mouth piece (also have a mask with Mk "IV*" mouth piece and a few with Mk "V" mouth pieces.) I would love a Mk III but they are as rare as rocking horse poop, fantastic find with that one!
sorry about the quality of the pictures.
Thanks for sharing the images, these early orange rubber MkIVs are very few and far between in such good condition. For some reason that particular type of rubber doesn't appear to have stood the tests of time very well.
These early MkIVs existed in many variations, the earliest examples being made in orange rubber as previously shown. The first models also had the exhale valve guard secured by a small nut secured by a very small split pin, which was later changed to the more familiar cone shaped nut used on all subsequent MkIVs and MkVs.
MkIV with EA Filter as used by the BEF, this one is made from orange rubber and features the nut and split pin on the exhale valve guard.
MkIV in its standard configuration, again made from orange rubber but with the later cone shaped nut.
MkIV, identical the one above but made from black rubber.
MkIV, again made with black rubber but with a longer tube. These were mainly used by the Royal Navy.
Thanks for sharing your photograph, definitely an interesting one! I'd concur with it being from the 1930s, as the MkIII was issued to other organisations when it was withdrawn from military service and replaced by the MkIV, the transition was completed fully by around 1936 if I remember rightly.