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Invac PK-244

This is an Invac photoelectric encoder keyboard, almost certainly model PK-244 as it appears to be identical to a confirmed PK-244 (although these units have 49 keys instead of the supposed 44). The keyboard is enclosed in a unit that contains additional functionality, including a pair of Burroughs B-8971 Nixie tubes.

The photographs are archived from an unknown (now deleted) eBay listing (number 192792010945), captioned “1960's Mechanical Keyboard Invac Photoelectric mechanical with Nixie Tubes”; it sold for $1,500. The seller’s description was archived within the February 2019 Geekhack topic [SOLD] 1960s Invac photoelectric keyboard (where the sale price was listed):

[This is] the only 1960's keyboard I've been able to acquire. The 1970's are near impossible but 1960's simply don't exist. They're all in museums or were recycled long ago. Hand routed PCBs, Nixie Tubes and mechanical wizardry that always reminded me of a German enigma machine.

The keyboard was supplied with an Invac flyer that had been printed after the seeming acquisition of Invac Corporation by Digitronics Corporation; it has been incompletely stamped by a date in 1969.

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Internals, front view
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Internals, side view
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Cover of the flyer; the remainder of this particular flyer has never been made available online.