On the page http://vremya4e.com/interes/16025-temy-sochineniy-dlya-gimnazistov-v-carskoy-rossii.-eto-vam-ne-ege.html there is an image of a handwritten essay from 1917 whose title begins with Развитие, but the written form of з looks quite different from its standard cursive form today. It looks like the cursive form of s in English. (This letter appears several times in the essay itself, e.g., in оказалось and, in the footnote, назад). The Wikipedia page for the Cyrillic letter S/s (dze) says this letter was eliminated from Russian in the 1700s, but if so why would this letter be appearing here? Maybe it is just an archaic written form of з, and if so when did it disappear?
I would also be interested to know if this unusual way of writing з was used by other people back then too, if someone has access to scans of century-old written documents.