Yes, plack is in the scrabble dictionary.

What Plack means?

1 : a small billon coin of Scotland issued from James III (second half of 15th century) to James VI (early 17th century) also : a corresponding unit of value half-plack coin. 2 archaic : a paltry bit : trifle.

Are plaque and plague spelled the same?

is that plaque is any flat, thin piece of metal, clay, ivory, or the like, used for ornament, or for painting pictures upon, as a slab, plate, dish, or the like, hung upon a wall; also, a smaller decoration worn on the person, as a brooch while plague is the bubonic plague, the pestilent disease caused by the virulent ...