This is an Encore series single arm crank operator used to open and close casement windows.
The manufacturer (Truth Hardware) calls this operator right handed: The handing is determined by the side the hinge is on when viewed from the outside. See SWISCO product 39-457 for the opposite handed version.
11/32" spline; handle and cover sold separately.
Mounts to sill
11-3/4" long arm, measured from wheel center to gear center.