Mannheimse
Mannheimse refers to something related to Mannheim, a city in the southwestern German state of Baden-Württemberg. The form is not part of standard modern German usage; the typical demonym for people from Mannheim is Mannheimer, and the corresponding adjective is Mannheimer. Consequently, Mannheimse appears primarily in historical texts, regional dialects, or in loan contexts where a non-standard form has been preserved.
In usage terms, if encountered, Mannheimse would function as an attributive adjective meaning “from or of Mannheim”
Mannheim (the city) is located at the confluence of the Rhine and Neckar rivers, in northern Baden-Württemberg.