The recent implementation of three-dimensional microwave cavities coupled to superconducting transmon qubits has led to dramatic improvements in qubit coherence times . Besides the superconducting aluminum cavities that have been used in many such measurements, other recent experiments have utilized copper cavities  with coherence times now approaching 0.1 ms. We are investigating the effects on the quality factor for three-dimensional copper cavities that have the cavity-wall surfaces electropolished and coated with a superconducting tin layer. The copper base provides a good path for thermalizing the cavity walls and qubit chip, while the surface treatment reduces the microwave loss. We have measured a superconducting transmon qubit in such a cavity and we report our low-temperature coherence results on the same qubit and cavity measured in two different labs. © 2013 IEEE.