Langworthy made chips too (plastics), but the clay chips they sold were manufactured by Burt Co.
Originally located in Detroit, Langworthy & Co. started manufacturing chips as R.T. Plastics after moving to Las Vegas in 1962 (and later opening the Gamblers General Store across the street from Spinetti's).
Interesting. So when the order card has “Langworthy & Co. Order” typed on it, but the card has “The Burt Co.” stamped in the lower right corner, I guess that means they were a Burt production ordered via Langworthy.
Note: Extra Heavy!