Everything is hand lettered calligraphy.
To approximate the _S_ with a font you could look at those tagged uncial, Lombardic, medieval, illuminated, Irish, medieval, etc.
Don

A few fonts with simplified versions of the capitals: Initials Gothic C https://www.myfonts.com/fonts/alterlittera/initials-gothic-c/
Medieval Caps BA https://www.myfonts.com/fonts/bannigan/medieval-caps/ Merona https://www.myfonts.com/fonts/intellecta/merona/ Gothic Initials Three https://www.myfonts.com/fonts/gallofonts/gothic-initials-three/
Don

More: Hours in the Rain http://www.dafont.com/hours-in-the-rain.font?fpp=100&text=BS Queen & Country http://www.dafont.com/queen-country.font?fpp=100&text=BS Gotische Majuskel http://www.dafont.com/gotische-majuskel.font?fpp=100&text=BS
Don

Worth browsing: Some initials digitized by Dick Pape http://luc.devroye.org/fonts-72670.html
Don

Camelot Caps by House of Lime http://www.fontspace.com/house-of-lime/camelotcaps Used to be available at the House of Lime website. Moved? Gone/
Don

This could perhaps be the closest I have seen to your _S_: Genzsch Initials from House of Lime http://www.fontspace.com/house-of-lime/genzsch-initials
Don

If you want the detail of the fancy initial caps -- too complex for a font -- I recommend a visit to the Aridi website. http://www.aridi.com/index.php/about-aridi-arts?id=41
Note that the names are confusing, but the products are excellent.
Don

Thanks donshottype for going to all the trouble of posting all of those links, I appreciate it!

Less to the point than Don’s detailed list, perhaps here you can find something, not necessarily similar, but in the genre: http://www.dafont.com/theme.php?cat=404&text=BS+bs&af=on

Add to the list: Goudy Text MT Lombardic Capitals http://www.myfonts.com/fonts/mti/goudy-text-mt/
Don