-----
Thanks very much for sharing this interesting find with the forum!
Hercules one of five or six German cycle marques which come from in and around Nurnberg. It is unrelated to the British Hercules. Motor cars were also produced.
Hercules Werke AG, Nurnberg, Germany The German Hercules company was a completely separate bicycle and motorcycle manufacturer, with only the name in common with its British counterpart. They made …
herculesmuseum.wordpress.com
en.wikipedia.org
Appears to date from somewhere between mid-1970's and early 1980's. You may have discovered a date marking on the shell of the rear hub. It is likely to be a Fichtel & Sachs product whether badged as Torpedo, Centrix, Durex, etc.
Here is a guide to reading the date markings:
View attachment 1811078
Yes, fitting on seat stay is wheel lock.
If you did not get the key do not press in the slider or you will be stuck.
Here are some similar fittings. They are pretty much standard on German & Dutch practical transportation cycles for adults.
This one is a proprietary design found on Monark & Crescent bicycles from Sweden -
View attachment 1811079
View attachment 1811080
The one on the Hercules might be termed the "pill box" type. There is also a widely encountered "horse collar" type -
View attachment 1811082
View attachment 1811083
View attachment 1811084
Hercules manufacturer catalogue 1982 -
Quelle: Heinz Fingerhut | Bereitgestellt durch Velopedia, das Onlinearchiv des Historische Fahrräder e.V.
velopedia.online
-----