Is there a name for this mark? It sits below a letter as a means of showing an abbreviation. (In this case, Established abbreviated to Estd.)
I've seen it used in the form below in place of an apostrophe for a contraction. Frequently, it's used to abbreviate William to Wm.
I know there's a diacritic mark called an underdot, but I'm not sure this qualifies as a diacritic since it's not meant to influence sound value of the words.
It's some sort of stylized period (full stop for my British friends). But, I'm wondering if there's a term for using it to raise the letter above it in this usage.