2 and 15/16" by 3 and 5/16" (base diameter/ height). The groove brow and groove lip have sharp edges. Profile closely matches Lima catalog no. 121. Closest to U-234 or U-236 but groove brow doesn't protrude on the Lima.

Correction: Elton Gish reports that it is an unlisted (not in is book) Lima with catalog no. 120, not 121, and is U-237.