During WWII (and afterward) the British used a black stove paint (called Suncorite) on small arms of their own manufacture, and many Enfield service revolvers, Enfield rifles, STEN guns, and BREN guns have it. Sometimes revolvers are stamped "wartime finish". Quick, cheap, and apparently it worked OK. The use of black paint on guns by the British army is an old story - they painted their muskets with black paint (wood and all) during the Crimean War to make them less visible to the Russians.
Back about 2 years ago, there was a mention about a pre-Victory with a Suncorite finish in the Victory thread:
"938830 5 inch , 38 S&W ctg. Suncorite finish. Gun is loaded with markings. Butt is marked with Canadian C with Broad Arrow, flaming bomb, and P.. Near grip hump on right is FTR, not dated. Curious mark shown in my photo above trigger guard on right that is somewhat similar to the Suncorite finished gun on page 110 of Charles Pate's book. This mark possibly was added after the Suncorite finish as the paint looks chipped by the marking. All serial nos. match including the smooth walnut grips. I thought this surprising on an FTR gun! No US property mark."