The marking is pretty unambiguous since it not only shows the ~ symbol for AC but explicitly states the frequency range (50-60Hz).
There is a chance that a 12V DC power supply may work but that is not guaranteed. Sometimes the AC power line is used to produce a clock signal and even more likely the AC may be used to produce 2 DC symmetrical DC voltages (+/- 12V).
Thanks everyone... now to get this guy the proper power it deserves. I damaged it's power adapter, so I am hoping to find the right thing to replace it with.