English: "Thor, der Donnergott". Frontispiece by Johannes Gehrts to Götter und Helden der alten Germanen : Der Edda nacherzählt by Frieda Amerlan (1841-1924, for the record).

I accidentally saved the original scan as a JPEG, but I scanned at 800dpi so doubt anyone will yell at me too much.

The yellow colour is most likely in imitation of German chiaroscuro woodcuts of the 16th and 17th centuries, albeit noone would mistake the woodblock engraving atop it for anything earlier than the 19th century.

The book does not list a date in it, but the signature on the image is dated [18]90, Worldcat gives dates of 1900 and 1912, and given this is a rather high-quality edition, I'm going to presume it would have predated WWI and the economic collapse that followed. A variant, redrawn by Eduard Ade, is available at File:Thor_by_Johannes_Gehrts.jpg and was published in 1901, so I suspect this tends towards the earlier side of the range.