This is a Dutch “pot” (1640-1650). Or rather, I think that is the text I spoke into my camera (that's how it works nowadays) until I was informed: "this helm is not a 17th-century dutch 'pot', but the bowl of a late 15th-century sallet, West European (perhaps German or Austrian), ca. 1470-90." This comment sounded so professional I think it must be right.

The viewer next asked about my having pictures of crossbows: no, sorry.