Barney accepted Clark's offer to sell to him a portion of Clark's coin collection. Clark forgot at the time of the offer and acceptance that her prized $20 gold piece was included in the portion that she offered to sell to Barney. Clark did not intend to include the gold piece in the sale.
Barney, at the time of inspecting the offered portion of the collection, and prior to accepting the offer, saw the gold piece. Is Barney entitled to the $20 gold piece?