I found one of those old German printings sheets called Münchener Bilderbogen — they were the equivalent of a comic strip in the 1890s. There was a a story in there with a picture of three robbers. They inspired my story, which developed as I started drawing. So I must say that originally those three robbers were not my idea. Original ideas can always be traced back to something. We are all influenced by something, and then we translate it and transpose it into something else.
Emphasis mine. (Steal like an artist.)
I tracked down the original sheet he was talking about:
Here’s a side-by-side comparison of a page from the book with a panel from the sheet:
And a close-up of the original robbers: