“The Kirk mask was discontinued in [a single year].”
Unsettled
Correction
Sources disagree: 1976 (Propstore) versus about 1979 (fan sources).
What is agreed is that the license had lapsed and the masks were out of production by the time Halloween made the mask famous. Don't quote a single year.
What people actually said
“By the time Halloween became popular, the Paramount license had expired and the Kirk masks were out of production.”