What is the power plug in the photo called?

Apparently, there are HP server power supplies that have a non-standard connection.
They are found on ParallelMiner as KT-1200-200V-1 for example.

We use a custom 12inch power cord to bypass the proprietary AC plug

Behold the custom cable:

C13UNIVERSAL

It's just a cable with quick-connects.

Apparently this is the 277VAC version of the power supply:

HP 1200W Common Slot 277VAC Hot Plug Power Supply Kit (717359-B21).

The plug and socket are called LS-25 and LS-26. (an adapter is sold by stuartconnections)
HP also sells adapter TK801A and TK802A.

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(source)

If you take a look at IEC World Plugs, it does look similar to an IEC Type I male connector, however, one of the blades is rotated 90 degrees.

enter image description here

My guess is that it is a proprietary connector to avoid the possibiility of connecting the supply without a cable from the manufacturer.

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