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Another mystery object

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In the early 1920s the Air Ministry Director of Technical Development produced standards in the DTD series to cover aeronautical requirements not already covered by an existing British Standard.

The earliest reference I can find to DTD 133 is Sept 1930 when it was split to form DTD 133A. As yet I have  not found a reference of this time to DTD 133B.  No doubt it is related to the parent specification that covers aluminium not suitable for pistons. So if the frame is of aluminium rather than steel it suggests it is for airborne use to enhance sighting in perhaps dim light?

I assume the lever in front of the brow rest allows the green or red filter to be flipped between the sight frames?

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In with these other specifications, I suspect DG 4 is Defence Guide DG-4.

I believe that Defence Guides were introduced in the 1960s. Many Defence Guides when updated appeared as Defence Standards from 1976 onwards.

For example:

DG-12 first issued in Jan 1969 after several issues, when in 1976 morphed into Def Stan 01-5

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Hi . I believe it's a AA site for gunnery training .you have the traditional gunfire in the centre . The red and green lenses create a basic 3 d effect. So you could project a film of aircraft in 2d on a screen or some and the lenses would create a depth effect useful for AA gunnery ..

It's missing the telescopic sights which would look a bit like trench sights but you can see the headrest and a side pad for the head ..the right hand side is likely to have a Audible ear piece for effects and instructions...






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