It is a "Governor" as Fred said. It's used normally on Big Bolt engines to control engine over-speed conditions. The side plate (flat semi-oval plate attached with screws) under your finger tips probably is stamped CHEVOLET VARI-SPEED. See the attached pic below. There are probably other makes/manufacturers, but that's the one I am familiar with.
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Last edited by Peggy M; 05/30/2024 11:47 PM.

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)