Now I can see what marks you meant and attach the pics. As far as I could gather from the heap of images there are at least two different marks. Based on the fact that I date the Mörkö gun to ca. 1430, they could be either High Gothic housemarks carrying a certain symbol, owner's or maker's marks (they are chiseled, not casted) or may have apotropaic (warding off evil) function quite common of those superstitious times; the bearded head in high relief on the Mörkö gun, in all proboability, served the same purpose. On the other hand, the mark with the M shaped base could also be a simple way of early numbering - cf. the numbering on the hook of my huge Nuremberg bronze Doppelhaken
- , and it may as well represent the stylized tree of life. The other mark, in the shape of an arrow, might be a workshop mark denoting that that worksphop had formerly manufactured arrow heads.
Just to demonstrate how dangerous any statement on that early field may be, I must correct myself for saying that marks on guns and related arts and crafts generally do not appear before the beginning of the 15th century. Let me just mention the marks and inscriptions on sword blades, or the little arrowhead mark on my small Aljubarrota barrel of ca. 1360-80.