What type of power cable for Krell, confused

This may be a simple question but I have several Krell amplifiers that were left to me from an estate. I have no power cable for them and have looked to see a connection that I am not familiar with. Typically I am used to seeing the 3 prongs that slide into the power cable positioned vertically, on the back of the Krell amplifiers I have, the 3 prongs are all positioned horozontially? What type of power connection is this?

Thanks