Not sure that all those variants "count", but to my understating there are six of them to the word clipeus:
Those different variations had raised several speculations in the ancient's minds with respect to the meaning and/or etymology of those different terms - even to extant of self-contraction (...
I think your question has both Latin and typographical elements to it.
You are correct in that Greek the letter sigma has two variants: ς, used only at the ends of words, and σ, used elsewhere which was then reflected in Latin cursive.
In Old Latin cursive "the letter s was written as a vertical downstroke with a small curve at the end of it, and a ...