I have had this tank for sometime. Having found the 6pdrs I glued them in. Don’t remember the manufacturer, though it may be Minifigs! When I was planning some Operation Sealion games back in the 1990s I intended that the Home Guard would make use of a museum Mark IV Male tank. I mentioned this also in an article I wrote on a French themed Operation Sealion, Otaire de Vigneur.
To add a bit of diversity to my games, I also have one of Minifigs’ World War One British tanks, for use by a Home Guard unit (stolen from a local museum no doubt).
Now when I wrote that article and bought the miniature it was only an assumption and what I thought would be a nice idea, and probably had no basis in truth….