Another early one, but probably not THE earliest, is the Bank Club Reno series on the "S" mold, which includes a $1 black chip (below, from ChipGuide). Listing says 1934, so the C&S chips likely beat it by a few years. Bank Club Reno was supposed to have had illegal games in the basement prior to 1931, then came out in the open after 1931 legalization. Same with the Palace Club, I think. But my bet is still on one of the C&S chips from elsewhere.