Different models of McIntosh MC-75?

New to forum and thank you in advance for any and all information. I have a pair of McIntosh MC-75 amps. Have searched the Internet for various models but have never seen the ones I have - All original but on the front panel mine has all the familiar inputs / speaker terminals, etc, but no line voltage switch next to the 117V/300 watt input. Have not been able to find one designed like this. Any Information would be helpful.. Thank you in advance. MC-75 / Electrocompaniet Preamp / Kef speakers / Velodyne Sub