A symbol on page 302 of Goldblatt's "Topoi [. . .]".

Question

I'm reading Goldblatt's "Topoi: A Categorial Analysis of Logic."

There's a symbol I don't recognise on page 302 of the copy with International Standard Book Number 0-486-45026-0. It's in the definition of a natural number object and resembles a cross between $s$ and $\sigma$.

For lack of a better format to show you what it is, here is a picture:

.

I have tried using Detexify but to no avail.

What symbol is it?

Please help :)

Answer 1

That symbol looks like a cursive letter s (lower case).