TgO Lev27:25 :וְכֹל פוּרסָנֵיה יְהֵי בְסִלעֵי קוּדשָא עַסרִין מָעִין הָויָא סִלעָא‏ : all its evaluation should be with the sacred sela, the sela being 20 m'-coins
See the entire entry for māˁā n.f. a weight, a small coin