That's the ISO version of designation for a (in NASI spec) TCMT32.51 insert.
T - Triangular shape
C - 7º side clearance angle
M - tolerance range on I.C. size, tip distance & thickness, you want the values in inch or mm?
T - single-sided screw down, chibreaker edge, hole 40-60º double angle countersink
16 - long edge length of triangle shape, 16mm
T3 - 4mm thick, or 2-1/2 "sixteenths" of an inch. No idea why the T or the 3 is used in the ISO designation, but is used primarily on screw-down inserts
04 - tool nose radius, 0.4mm or about .0156"