I had never heard about this alternate form of piano notation before coming across a score using it today. Klavarskribo was developed around 1930. You can read more about it in Grove (in Oxford Music Online for U of I patrons) or in Wikipedia (for non-U of I patrons).
Here is a the first page of Beethoven’s fifth symphony arranged for piano by Liszt in regular notation. You can make out the famous theme pretty easily. (Click on images to enlarge.)
We have about about two dozen klavarskribo scores in our collection and one book about the system.