The appeal board may, in its discretion, consider in the determination of an appeal any official records or reports on file with the city board which relate to the appeal; provided, however, that not later than the 15th day after the date of filing of the last filed appeal paper and prior to the consideration of such records or reports, the appeal board shall file an order (a) advising the parties as to which records or reports it intends to consider; (b) permitting the parties an opportunity to examine and copy them; and (c) setting a date by which the parties must submit any affidavits, memoranda or other papers concerning such records or reports.