7/8" keyseat cutter, 5/32" face width, 12 flutes.
A keyseat (Woodruff) cutter for milling keyways, slots and undercuts. It cuts 7/8" diameter with a 5/32" face width on a 1/2" shank, 2-5/32" overall.
The staggered teeth cut on the periphery, so the tool feeds sideways into an existing opening rather than plunging.