Windows – How to determine what kind of key Win7 was activated with (retail or volume license)

I am working with a non-profit organization that just had a pallet of computers donated to them. The computers have had their hard drives wiped so there is no operating system installed. They are a small agency and they do not have an IT department, so I have volunteered to set them all up. Since the new computers will be replacing their existing equipment, my plan is to pre-stage them in my lab and then transfer the activation keys over once I deploy them (this is perfectly legal by the way).

All of the old computers have Windows 7 Pro installed on them. The problem is that they do not know how they acquired their licenses. Windows 7 Pro has both a retail channel (which only accepts retail keys) and a volume license channel (which only accepts KMS/MAK keys). I have access to the install media for both, but if I stage these computers with the wrong one, I will be in for a rude awakening when I go to transfer the licenses over and the keys don't work

Is there a way to tell what kind of key was used to activate a Windows 7 license?

NOTE: This is not a question about proper licensing or product licensing in general. It is a technical issue related to product activation.