Black Bands on Barrel and receiver

I just recently purchased an Winchester 1917 and when I was disassembling it for a cleaning before shooting it for the first time I noted that there appeared to be some black paint on the barrel and the receiver. I have never heard of this and figured I would post some pics to see if anyone here knows anything about it. There also was a marking on the barrel that I have included to see if that helps. Thanks.

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I am not sure what caused the marking on the barrel, but the receiver shows the heat treatment.
John

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Originally Posted by jamie5070

I am not sure what caused the marking on the barrel

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Those look like the shape of the front band being left on during refinishing (parkerizing)...