Who is Kelvin Kelstein from Killing Floor and what is their importance?

Kelvin Kelstein worked with Walter Bartholomew in the second World War on a project designed to destabilize the German economy. As a result of this work, they both became obsessed with the history of forging and the interest followed them into private life. Kelvin and Walter co authored a book that rapidly became the bible for the Treasury Department where counterfeiting was concerned.