FWIW, the first number is the inscribed circle in 1/8s, The second number is the thickness in 1/16ths and the third digit it the corner radius in 1/64s of an inch. So a TPG221 is a triangular ground positive rake insert, 1/4" IC, 1/8" thick with a 1/64 corner radius. TPG 322 is 3/8" IC, 1/8" thick with a 1/32 (2/64) corner radius, etc. That looks like a TPG22x series to me.