Yes, I have been looking for months.
The earliest absolute proof I have for the existence of Stud Playing Cards comes from 17 feb 1937. The ad seems to indicate that they are a new brand. I'm sure their "Smooth, linen finish..." means they are a
slick Linen Finish, as opposed to a Smooth Finish.
There are a LOT of ads for Studs in 1937, from Illinois and Missouri to the earliest example I've found from Idaho.
I find it very interesting that the back shown here is the same as the modern back. (I thought the "multiple windmills" back preceded the modern one.)
Quick reminder to those searching for tax-stamped Studs - UPC codes and tax stamps
NEVER coexisted! There's a gap of
10 years between them. There are pictures of UPC / Tax stamp Studs even here on PCF. Be warned. From "Studs came out around 1980" to "These tax stamps and UPC decks are legit," there's a bit of misinformation.
Attached, find a full page Walgreen's ad and 2 zoomed sections. The Post-Register - Idaho Falls, Idaho - 17 february 1937.
@Don - It does seem old enough to appear in Hochman's.