Alternator Output Amps

[captain465]

Maybe a very basic question, but I would like to know how one can tell the rated output of an alternator without actually running it. Are there any identifyiing numbers or codes to look for? Also how do you tell who the manufacturer is , and if it is internally or externally regulated?
I would like to get a extra alternator to use as a spare (don't ask why)and would like to be able to verify all the pertenamt information.

[svaletheia]

Often from the outside there is not an easy way to tell - there are so many kinds and makes out there. However Balmar units are typically white casings and probably have Balmar stamped on them somewhere. The ratings are almost never published on the casing, however, and are a factor of both the components internally and the ability of the unit to properly cool itself. If you have a picture someone here might have a similar unit and be able to tell you its specs but I don't think there is any sort of forumulaic manner in which to verify information that holds true across all alternators without spinning them up and potentially pushing them past their limits.