The brass bridge saddles standard on older Broadcaster’s, No-Casters, Telecaster’s and Esquire’s used a 5/16″ in diameter free cutting brass cut to the desired length and tapped 6/32″ in 3 places. The two vertical tapped holes are for height adjustment and the horizontally tapped hole is used for the string intonation. The early saddles were slightly flattened on the bottom to allow lower action if desired.

I’ve seen saddles made out of steel on very early instruments, and the early Precision Bass (often called the Telecaster Bass) used two bridge saddles made out of 1/2″ round and machined phenolic. It would work for a period of time, and then the pressure from the strings would cause the phenolic to split, warp or collapse.