Engine Casing Clamp Plates.
Fits 1919 to 1929 61" & 74" J & JD Twin Motors.
Harley Davidson started using these plates around 1919. The plates were added to help keep the motor from working its way down on the motor mounts. It is quite common to find these on models earlier than 1919. Many owners installed them and the longer mounting bolts as an 'upgrade' to their motorcycles.