books and elsewhere for some details. The name "Merkur" has been applied to several German machines over the years, but I haven't found this one.
The "Einwurf" lable just means "coin entry".
Tura was the main German manufacturer of American style bandits (originally, C M Schwarz, Leipzig). I think the mechs. are more or less copies of the Mills, in which case the Owners Pictorial Guide to the Mills Bell could be a helpful workshop manual. You'll find pennies for sale from the PennyMachines Spares shop.