53 Pa. Stat. § 16952
The original books, when made, shall be kept in the fire-proof of the department of surveys of the said city, and a duplicate set thereof shall be placed, by the chief engineer and surveyor, in the office of the city commissioners, and be there safely preserved in the fire-proof. And the said chief engineer and surveyor shall keep up the books in his office, so as to show at all times who are the owners of the lots on the plans, and before the annual meeting of the board of revision, for revising the valuations for taxation, shall cause the books in the commissioners' office to be brought up to that time; and such books shall be kept in such manner as not to destroy the evidence of the ownerships at any previous time, but by additions which will show the subdivision of property, and the owners thereof, as transmissions of title may take place. And the said chief engineer and surveyor may furnish copies of the said books, or parts thereof, for such price as may be fixed by councils, for the use of the city; and his certificate shall be received in evidence, as and for such proof as the assessment books would be; and lithographed copies of the said books may be multiplied and sold for the profit of the said city.
53 P.S. § 16952