Charles I Half Groat - Is This A Triangle Mintmark?

[vs1969]

Good afternoon to everybody,

I've got a half groat of Charles I with a mintmark partially off flan on the obverse and completely off flan on the reverse.

From what is left I would conclude that it looks similar to a triangle, but other triangles I've seen online (and in books) are

"wireframe" and this one seems to be filled. What could it be?

Thanks in advance.

[Rob]

Yes it is.

[vs1969]

Thanks!