This is a metal rail anchor. The anchor measures 1.5" (h) x 7" (w) x 4.5" (l).
According to museum volunteer Tom Peyton, the “double spring type anchor mounts under the rail and clipped over the foot of the rail to hold the rail in place.
Lexicon
Nomenclature 4.0
Nomenclature Primary Object Term
Component, Track
Nomenclature Sub-Class
Rail Transportation Accessories
Nomenclature Class
Rail Transportation Equipment
Nomenclature Category
Category 07: Distribution & Transportation Objects