As a complement to the "indicator-frame" here is the references of the cited
book :
        The inventor is Dr Julius Paschke
 
        The book : "Der Neue Baurahmenimker" by Maria E. Paschke (1952)
        French edition : "Le cadre-temoin", J.Mosbeux, Bruxelles, ed. (1973)
I don't know if an english edition was published.
 
Regards.                      Jean-Marie.