Watch List notes:

MACEDON, Kingdom of, Antigonos Gonatas, silver tetradrachm, 277-239 BC, (issued 246-229 BC) (15.38 g), struck at Pella, issued c.272-239 B.C., obv. Pan's head to left, with pedum on shoulder, all within Macedonian shield, rev. Athena Alkidemos advancing to left, with thunderbolt and shield, Macedonian helmet in field to left, KT to right, to right **BASILEWS*, to left **ANTIGONOU*, (cf.S.6783, cf.SNG Greece (Alpha Bank) 983, cf.SNG Ash 3260, Seyrig 16 59-65, cf.Mathiesen ANS MN 26 [1981] p.111 [for KT], HGC 3, 1042). Lightly toned, fine and very rare variety.

Ex Dr. L.J. Sherwin Collection, from Robert Loosley (Antiquarius), 30th May 1989, from list 18 (item 32), previously from Baldwin's London.
The symbol IT is apparently the reversed letters to TI which is well documented, IT has no examples in Coin Archives.