Volt and amp ratings for surplus steppers

Newbie questions, and apologies for asking basic stuff. I did a
search of old messages, but apparently didn't use the right search terms.

I have a number of steppers from printers and other sources. Some are
obviously too small for CNC use, but others might work. However, I'm
confused by the stated volt and amp ratings painted on them. Size
doesn't seem to relate directly to their volt-amp ratings.
Do large, weak steppers exist, possibly from older designs?
Does the volt and amp rating state a maximum for each winding, or the
total unit, or a stall current, or...?
Can a 3 volt stepper be operated at higher voltages (and consequently
higher current) as it seems from the posts I've read?
How does one identify the capabilities of a surplus stepper?
Is this in the archives, and I missed it?

Thanks for helping a beginner,
Rex