I found something similar once. While testing a then-new feature of image search I fed in a picture from one of my pages. The ultimate source was an e-book whose printed original is in the public domain. Looking more closely at one hit, I found their image captioned "from Handbook of Widgets by John Kilroy. Used by permission." I really, really wanted to write and ask-- in the spirit of polite inquiry-- how they contrived to get the permission of someone who died in 1877.