53 Pa. C.S. § 8868
(a) Election.-- A city in any county to which this chapter applies may, by adopting an ordinance, elect to become subject to this chapter. A copy of the ordinance approved by the mayor, or other comparable official if so required under an optional form of government or home rule charter, and duly certified, accompanied by a statement of the vote thereon, with the names of the members of council voting for and against the ordinance, shall be forwarded to and filed in the office of the Secretary of the Commonwealth, and, when so filed, the Governor shall under the great seal of the Commonwealth certify the acceptance of the provisions of this chapter which certificate shall be recorded among the minutes of the council and in the office for the recording of deeds in the proper county. A city that has previously opted to become subject to the act of May 21, 1943 (P.L. 571, No. 254), known as The Fourth to Eighth Class and Selective County Assessment Law, or the act of June 26, 1931 (P.L. 1379, No. 348), referred to as the Third Class County Assessment Board Law, shall continue to be subject to this chapter.
(b) Result.--Upon becoming subject to this chapter in accordance with subsection (a), the property and persons subject to and exempt from taxation in the city for city and school purposes shall be designated in accordance with this chapter, and the assessment and valuation thereof shall be done only in accordance with this chapter and by the officers designated in this chapter. If a city in accepting the provisions of this chapter elects by ordinance to adopt an established predetermined ratio different from that used by the county, then the city shall apply the ratio selected to the actual valuation supplied by the county to determine assessed value for tax purposes. The established predetermined ratio selected by the city, if different from the ratio selected by the county, may be set at any value up to and including the actual valuation supplied by the county.
(c) Alternate ratio.--If a city accepts this chapter in accordance with subsection (a), all the provisions thereof shall apply to the city except that a city may, by ordinance, elect to adopt an established predetermined ratio different from that used by the county.
53 Pa.C.S. § 8868