This is a supplement to my monograph, “THE TYPOGRAPHIC OVERPRINTS OF THE 1919 KRAKOW ISSUES OF POLAND” which was issued in 1990. On page 15 of the monograph, I stated the following:
"A possible additional method of examining these overprints would be to use an optical scanner to create a digitized version of each of the Austrian stamps that were overprinted. Then by electronic comparison using an appropriate software program, the background could be subtracted from the scanned digital information of an overprinted stamp to yield a clean representation of the overprint on a computer screen. I have not yet attempted to use this approach.”
I have now developed such a method and it is the intent of this supplement to detail this procedure which involves the use of a computer, flat bed scanner and appropriate computer software.