Section 7. In all controversies in which application is made under the preceding section, each party may, in writing, nominate fit persons to act in the case as expert assistants to the board, and the board may appoint one from among the persons so nominated by each party. Said experts shall be skilled in and conversant with the business or trade concerning which the controversy exists; they shall be sworn by a member of the board to the faithful performance of their official duties, and a record of their oath shall be made in the case. Said experts shall, if required, attend the sessions of the board, and under its direction shall obtain and report information concerning the wages paid and the methods and grades of work prevailing in establishments within the commonwealth similar to that in which the controversy exists, and they may submit to the board at any time before a final decision any facts, advice, arguments or suggestions which they may consider applicable to the case. No decision of said board shall be announced in a case in which said experts have acted without notice to them of a time and place for a final conference on the matters included in the proposed decision. Such experts shall receive from the commonwealth a sum not exceeding thirty dollars each for every day of actual service and their necessary traveling expenses. The board may appoint such additional experts as it considers necessary, who shall be qualified in like manner and, under the direction of the board, shall perform like duties and be paid the same fees as the experts who are nominated by the parties.