How do I test a display? From an iMac intel 27"?

jerrypaulson, that will depend on how well you are in reverse engineering. Since you did not provide us with any information about any markings on your LCD, start with this. Get the datasheet for the LG LM270WQ1 LCD - P/N:661-5568 which is the display for the iMac 27" 2.8GHz Core i5 (A1312) - Mid 2010 from here. Check the controller pins and compare those to the computer that you are going to test it with. It will all depend on what you have to test it with, and will require you to find the proper pinouts, as well as making sure that you have a proper driver board. You will most likely not getting it connected as a second display, but you may get to test its functionality. If that is not the right panel, you will have to supply us with more information about the one you have. Remember, that even so it appears as if they are proprietary, there is other equipment that uses those panels.Hope this helps, good luck.