Where a principal claimed that its broker had been notified of its custom to give only quit-claim deeds to purchasers of its real estate, evidence to show that after its refusal to give a deed with warranty, it offered to give such a deed if an increased price was paid, was admissible to show that no such custom existed. Beach v. Traveler's Ins. Co., 73 Conn. 118, 46 A. 867.