I know the meaning of pe-nun on the headstones. One of my great grandmothers has pe-tav. Her husband's stone has pe-nun, so I'm puzzled as to why the family would change it for her. In fact, it's the only one I've seen with that inscription. I do know it also means "here lies," but I wonder if there's a nuanced difference. She did die tragically, as I found out, if that could explain anything.

Mal Blier

Are you sure it's pe-tav and not pe-tet
פ"ת
פ"ט

--
Odeda Zlotnick
Jerusalem, Israel.