AWOL:
I'm curious - what would you pay for one of those (it's just that I've got a cupboard full of 'em...)
$2 of course!
Can't go overboard about these things!
You are lucky then, they are ace keyboards - all the keys in the correct places (not fussing about Prt Scrn, Scrlk and Pause), smallest footprint possible and the most useful "Space Cadet" keys, notably instant mute, volume control (knob), calc and some navigation keys I haven't developed the habit of using as yet.
My keyboard crate (wherever I have put it) contains mostly older ones such as "Gateway". I am aware that the going price for a SK-8135 on eBay is about $5 or so. I wouldn't go quite that far (unless I suppose, they were genuinely new and unused).