25 Pa. Stat. § 2095
The commissioners for the city of Philadelphia shall provide a fireproof room or vault, in the public buildings of the said city, or some other suitable place, at which the judge of the elections, after the closing of the polls, and the requirements of the law have been complied with, shall forthwith there deliver to the mayor and recorder of the city of Philadelphia the said ballot boxes; that the said room or vault shall not be accessible to any other person than the mayor and recorder aforesaid, who shall be present and receive, at the said room, or vault, the ballot boxes from the return inspectors as aforesaid; that the mayor and recorder aforesaid shall not take or open, nor permit to be taken or opened, any ballot box deposited as aforesaid, for the space of one year after the same has been therein deposited, except when they shall be called upon by some court or other tribunal authorized to try the merits of such election; and after such trial or investigation it shall be the duty of the mayor and recorder aforesaid to have said box or boxes returned and deposited as aforesaid.
25 P.S.§ 2095