It's also not a ligature for sz ("Amtszeit"), although it has developed from one (of the long s and the tailed z, see https://en.wikipedia.org/wiki/%C3%9F )
I like that the information loss in toUpperCase() is gone now in this case, so I am all for it O:)
If you squint and your font permitting, ſz should look more like ß.
FRAKTIONSZWANG FREIHANDELSZONE KONFISZIEREN [...]
A lot of them are combined, but still quite a few 'regular' ones
Abszeß - Adoleszenz - Disziplin - Eszett - Faszie - Faszination - Fluoreszenz - Koaleszenz - Konfiszierung - lasziv - Lumineszenz - Obszönität - omniszient - Oszillation - phosphoresziere - Plebiszit - Proszenium - Rekognoszierung - Rekonvaleszent - Szene - viszeral
Most of these actually are of latin origin. My favorite is obviously "Abszeß" - probably the only word in the german language that will show a non compounded co-existence of "sz" and "ß".
Nowadays it's written Abszess as the e is short.