It's Frank Adams gear. That piece has been installed and engergized since 1924.
There's still a lot of F A gear in use. They made good stuff.
The oldest gear I have seen is the Main Electrical Board on the USS Texas battleship in Houston. Built in 1911 by the J B Cutter Electric Co. of Phila. PA, the predecessor entity that became the ITE Circuit Breaker Company, then ITE Imperial, then Gould ITE, Gould, Gould Brown-Boveri, BBC Brown Boveri and is now part of the ABB Group.
The oldest switchgear and breakers I have worked on were made in 1929, ITE type LX 600A 600V 3 Pole. They're quite interesting. Built on slate, "hot-front" (meaning that all metal parts were energized), pull-down operator, carbon block arcing assemblies. Main contacts made of copper leaves, main contact pressure adjusted by removing or adding leaves. Some are the elevator feeders at a downtown building in Minneapolis, two were still in use at Ameren UE's Bagnel Dam in the Ozarks.
Sometime around 1920 the Reverse Current Trip devices were no longer supplied on one or two legs as the Power System became more reliable, but prior to that time, you got both overcurrent and reverse current protection on polyphase breakers.