I have just uploaded a video about a rare Jennings Witch.
I discuss how to identify the fakes as well as how the self loading jackpot works.
FYI, the Witch and all the Victoria (Model B) machines had a unique feature where the operator could specify how many coins the machine would load into the jackpot.
The video is at https://www.youtube.com/watch?v=yxC_lnCq39w