I knew there was a note in the book regarding prices, but couldn't locate it yesterday. See the attached picture.
In 1967, the conversion was 1:1 (1920 marks to 1967 dollars)
Per this website (
https://www.in2013dollars.com/us/inflation/1967 )
$100 dollars in 1967 is worth $888 in 2022.
So, 100 marks in the book is worth 888 modern dollars.