Many, many years later I still haven't found these. I've determined that it's likely, but not certain, the sheets were inherited by his son Gerald Krech. Gerald emigrated to England, with a brief relocation to Paris prior to WWII, and became a naturalized subject. He died in the Chelsea and Kensington district of London in 1991. The distribution of his estate never went to probate so there are no public records of what happened to it and none of his inheritors could remember the legal firm that handled his estate. He never married and his family and friends network was large and varied. If these cards still exist they are likely sitting in some private collection. Sigh.