I have quite a few mystery AC power BRICKS and transformer cords - meaning I have no idea what items they are suppose to power.   I've searched online by information printed on the labels (company, serial number, etc), but generally come up blank.  Any suggestions?  Much thanks!You could take post the company details and other information from the labels and also post PHOTOS of bricks, their labels and power connectors and post them for people to look at...

You could get a digital or analog multimeter and measure output voltages.

Many labels show rated output voltage and current e.g. 12v 2500 mA

You could do what I do, which is throw them in the trash. Unless you are an electronic HOBBYIST, in which case you will already know how to identify the output voltage and take a guess at the current (amps) rating, there is unlikely to be much USE for them. New equipment which needs a power brick will come with one, and the chances of you ever having a piece of equipment which could be USED with such a brick are very low.