sin-offering (n.) /propitiation/atoning-sacrifice (2x in GNT); 7x(LXX): atonement(Lv25:9, Num5:8); forgiveness(Ps130:4, Dan9:9); sin-offering(Ez44:27); guilt(Amos8:14). Gnadenstuhl, seat of grace; mercy-seat; covering of the Ark, used for the gift of grace(???).
mercy-seat (n.) A place of propitiation/expiation/atoning-sacrifice in-order-to appeases wrath and reconciles the parties. In the LXX typically refers to the mercy-seat of God's judgment. also ledge/threshold