I notice from the examples of his work on this page that his signature changed dramatically from work to work, but many look quite similar to the one on your picture. Some are written Kohler, some Köhler, both with the same style F, some have a different style entirely.
Thanks a lot!! The big differences between his signatures throughout his work threw me off but I'm happy to hear that you confirm what I was thinking. The website you've linked is a great help too!
Traditional Art
From dabblers to masters, obscure to popular and ancient to futuristic, this is an inclusive community dedicated to showcasing all types of art by all kinds of artists, as long as they're made in a traditional medium
'Traditional' here means 'Physical', as in artworks which are NON-DIGITAL in nature.
What's allowed: Acrylic, Pastel, Encaustic, Gouache, Oil and Watercolor Paintings; Ink Illustrations; Manga Panels; Pencil and Charcoal sketches; Collages; Etchings; Lithographs; Wood Prints; Pottery; Ceramics; Metal, Wire and paper sculptures; Tapestry; weaving; Qulting; Wood carvings, Armor Crafting and more.
What's not allowed: Digital art (anything made with Photoshop, Clip Studio Paint, Krita, Blender, GIMP or other art programs) or AI art (anything made with Stable Diffusion, Midjourney or other models)
make sure to check the rules stickied to the top of the community before posting.