Aberdeen Endowments Trust: Payment certificate book for contractors on the AET's estates The certificate stub records: date certificate made out; installment number; estate work carried out on; name and address of contractor; details of the work carried out; and record of payments and contract price. The certificates would have been signed by an Estate Officer and taken to the AET's Clerk, Treasurer and Factor for payment. Most of the book has been used but there are some blank certificates included. 1913 - 1916