The two "Mdina"s I've just put in look to me as if there was no vibrating element at all - just a straightforward scratch with a diamond tip...
The first one has suffered from age-related wear to the mark. It's on the bottom of an inside-out, which may help to put the proper size into perspective. The second image is of the "Mdina" in a polished out pontil mark on the bottom of an ink pot.
