Found this on a thread on Pinside "German built games typically had circuitry for EXTRA credits above and beyond the normal 2, 3, 4, or 5 plays for the right coin chute. This is because they had a 1 Mark and 2 Mark coin as well as a 50 pfennig coin (2 = 1 Mark). So, like the US Dime, you would get 1 play. For the 1 Mark Coin, you would usually get a bonus (just like the US Quarter ($0.25) giving 3 plays). They would give you an even bigger bonus if you wanted to invest 2 Marks at one time!"
Not sure if it will help you though
