Radius Rods. Two types (actually 3 counting the AR Early Model A)
Type 1 (earlier 1928-29) has a forged "Y" that attach to the backing plate with 2 bolts.
Type 2 (later 1930-31) has a "Y" formed of flat stock bent "in the flat" and like the other attaches with two bolts.
Either can be used. And are functionally equivalent. I have even seen "one each" on a car made of parts.
There is a "Left" and a "Right."
The typical fail is water getting into the low seam and "rusting out" the radius rod from within. If you hear flakes of rust floating around inside as you turn it end for end, expect the damage to be work than it appears.
Joe k