If you have an Amiga mouse, hook it up and hold down both buttons while starting up the 1200. This will bring you to the early startup screen and from here you can see if the Hard Drive is even detected.
If it is detected, then you will need your disks like you said to check further. If it is not detected, then make sure the cable is firmly connected. Power is through the cable, so the fact that it is spinning up is good, but if the connection isn't flush, then the pins on the other end of the connection may not be making the proper connection.
Either way, excellent find! I hope you can bring it back to life…
If you still haven’t figured out what the memory board is, try comparing it to pics on the Big Book of Amiga Hardware. Ok, never mind there a million and one memory cards on there! If you can take a pic of it and post it in the forums someone might be able to recognize it…
GOOD LUCK!:)