PA law - Deputy Appointment

If a safe deposit box is jointly held, can the appointment of a deputy be successfully granted by only one holder or do all holders need to authorize any deputy. This is not addressed within the S/D contract. Been informed this issue is a matter of state law but am unable to locate where it is addressed.

Can anybody help me out?

You might take a look at http://www.pacode.com/secure/data/061/chapter93/s93.22.html