Old IBM keyboards

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Yes, that is a terminal keyboard. It's not PC-compatible. To the best of my knowledge, there is no commercially available converter for it, although people have come up with various hacks to get this model to work with PCs and Macs. It's kind of a PITA to get it to work, apparently. (I personally have never tried, but if you're really interested, see this link, for example: XT/AT/PS2/Terminal to USB Converter with NKRO • deskthority.)

A good quick reference for the confusing array of "Model M" keyboards is available at Model M keyboard - Wikipedia, the free encyclopedia.
(To see the chart, be sure to press the "[show]" link in the "Part Number" header cell.)