Dang, I can practically smell the oil.
Which is pretty prominent with these, as there is a oiling pad above the feed slot to lube the cartridges.
The metal just above the feed tray is a little bit darker from having absorbed all that oil--but, it's more shiny, too, which kind of makes it an either/or for the modeler.
The cooling fins on these, up sloce always seem darker than the barrel--Burnt Iron to Oily Black, but scale effect would negate that a bit. They do all seem to have a highlight on the those fins, the sort of thing a rub with a pencil lead would render--but, it's a very skinny highlight.
The ammo for this had a gausey muslin carrier, but the smart people tell me the Japanese troopers nearly universally used the wooden box loaded with ammo in it's 40 round feeding strips.
For the seriously curious, the full-up squad for one of these is a gunner, the a-gunner, and three riflemen, with all of those designated as ammo bearers. If one notes the tubes on the front legs of the tripod, doctrine was that the MG squad would also keep track of a couple 2m wood or bamboo poles. if the MG needed to displace, the riflemen would come in, set the poles through, police up all the ammo, and then they, and the gunner on the back tripod leg, would pick the piece up entire and race to the new location.
The moniker "woodpecker" came from the steady rate of fire from the MG, with the pauses as more ammo strips were fed in.