I searched for "Pentax" in newspapers.com. The earliest search result was a classified ad, equivalent to PF's "Wanted Items" in the Marketplace, from the
Chicago Tribune dated 12 October 1933. It reads, "WANTED—DALLMEYER PENTAX LENS F. 2.9 10 in. focus or equivalent." In a classified ad in the
Los Angeles Times dated 1 June 1938, someone offered for sale a "10-INCH F2.9 Pentax lens; bargain $100." In today's U.S. dollars, that bargain price would be $1787.50.
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Just found another ad in
The Los Angeles Times dated 1 October 1944 offering a "DALLMEYER Pentax f2.9 4 1/4" in compur" [
Compur shutter]. The ad listed some other equipment and 120 film, too. The asking price? A trade for either a refrigerator or "a radio combo."