Need help! With IDing this British Holster (pics)

[dingus]

Heres a holster i just bought on Ebay its in minty condition, i have another more worn one just like it.
My Question is how or who in the British military wore these and when.
I was thinking Calvery or something where the straps would come into play?
1918 or maby Tankers in the 1940s ??

Any ideas ?

Click on pics to enlarge

 

[BEARMAN]

My guess is it would be mounted on the left side of a cavalry or maybe any officers SAM BROWNE BELT in place of a SWORD but using the same sword attachments. Time period about 1900 when pistols were replacing swords as a badge of an officer.

 

[Beater]

looks very similar to my 1914 canadian setup for the big .455 hand ejector model pistol

 

[green]

Have seen them in .38" and .455" sizes. Saw a picture of a Cdn General wearing one in Normandy 1944 on P37 web belt attached to two D ring sliders.

 

[dingus]

OK thanks im not sure if its a 455 or a 38 one the one i have now is a 455 one.
I bought it for $21 so im sure i will find a gun to fit it, once it gets here.