Almost certainly one of the many hundreds of thousands of S&W M&Ps furnished to the Brits in .38 S&W caliber ( or .38 British or .38/200 as it's also known). Thousands were purchased by English gun companies like Parker-Hale and Gogswell & Harrison after the war as surplus and converted to sporting revolvers.

Some had target sights added. Many had their barrels shortened from the original 5" length. A lot of them were reamed for the longer but smaller in diameter .38 Special. A number were converted to .22 caliber.

I don't see much collector interest in these guns and prices don't run real high. I saw a .22 conversion and thought it would be fun to play with but to me such a gun would be worth no more than $250 and I think the owner wanted more. I have no idea how well these converted guns work and shoot.

I just noticed you said yours has a 6" barrel. I would not be surprised if some 6" M&Ps were sent to England at the start of the war as they took anything S&W had in inventory but the usual length was 5" for the Brit models. Also possible that the .22 liner extends past the original muzzle by 1"? Can you see evidence of this happening?

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