Section 512. Assessors to Attend Appeals.--It shall be the duty of the several elected and appointed assessors to attend at the time and place fixed for the appeal from triennial and inter-triennial assessments for the respective ward, borough, town, township or district, to prevent impositions being practiced on the commissioners, acting as a board of revision, or the board for the assessment and revision of taxes, as the case may be, by the persons appealing.