The size of the old HP keyboard was becoming a bother, it's one of those full size keyboards with numpad and arrow keys besides the alphabeticals. Desk space is at a premium these days and additionally moving the right hand from the trackball to the keyboard over the numpad and arrow keys was an annoyingly long traversal.
I do own a smaller keyboard; a Filco Majestouch with MX Blue switches but it's just too loud for current circumstances and honestly the keys never really felt right. They're too light, requiring too little actuation force, less than the HP's rubber domes. My typing style can best be described as slow and heavy so I appreciate something that you can hammer on. Hence I needed to look for something small and quiet.
Pickings are pretty slim when it comes to smaller keyboards. If you look for tenkeyless and no arrow keys there's really only these tiny "travel" keyboards available and they're all of the chicklet design with shallow key travel. I prefer rubber domes over scissor switches and the old key style were the keys are tall and shaped like a trapezoidal prism with a dimple in the middle for your fingers to land in. On these travel keyboards the keys themselves were often smaller than normal keyboards and the layout cramped usually with tiny enter and backspace keys. What I wanted was something with at least 4mm of key travel and classical tall key caps. Basically my HP keyboard but with the numpad and arrow key parts cut off.
The only small keyboards with decent keys and layout looked to be mechanical ones and if you want those to be quiet the only readily available option was Cherry MX silent red switches. Since I didn't particularly like MX Blues the MX Reds didn't look that appealing considering their activation force is even lighter than MX Blues, only 45 grams compared to the Blue's 50g.
What I tried to find was a good old fashion rubber dome keyboard but those were rarer than hens teeth. There's the "Happy Hacking" keyboard with Topre rubber domes which looked really good but costs $250 which is a lot to plonk down when the $140 Filco was a bit of a let down.
The only thing that stood out after dredging ebay was the Sanwa Supply Compact Keyboard. Made in glorious Nippon it sported a somewhat unconventional key layout and some extra keys but over all it looked like a normal keyboard only shorter. Most importantly it explicitly stated that it used rubber domes so I ordered one.
It turned out really all right. The keys are the same size as on my HP keyboard - a KU-0316 - being 12x14mm and doing some not all that exact measurements with some calipers I got a key travel of around 4mm on the HP and a bit over that on the Sanwa.
The rated key travel according to the manual is 3.8+-0.3mm and the actuation force is supposed to be 55+-10g. That tolerance of +-10g for the actuation force would seem worryingly large and imply less than precise manufacturing but the keys all feel the same to me. Actuation force feels about the same as the HP but a lot stiffer than the Filco despite being only slightly so on paper.
The key caps are a bit looser than on the HP which makes the keyboard just a tad rattlier but it's pretty much as quiet as any rubber dome.
They have the same mushy rubber dome feel as the HP so if you hate those you're not going to like the Sanwa.
It has a large ISO enter key which I very much prefer to the smaller ANSI variety which was the more common one to find. There's even a full row of function keys. Even better was the price tag of $26 including shipping which is a pretty good deal. It would have cost about another $10 in import fees but fortuitously the package slipped through the greedy fingers of the customs agent and arrived unmolested by additional taxation. Pretty sure I have COVID to thank for that.
Only real downside is the superfluous Japanese keys, a badly placed up arrow key that you have to move over in order to hit right shift and a short backspace key. All of which can be solved through remapping some keys as described in one of the images below.
So if you're in the market for the same type of old crappy rubber dome keyboard that's been bundled with computers from HP or Dell or any major manufacturer since time immemorial but smaller I can absolutely recommend the Sanwa Compact Keyboard. It has the exact same keys and the exact same feel as one of those and despite being labeled as "compact" manages to not feel cramped or like the compactness was achieved on the cost of ergonomics.
Further plus points include the also full sized arrow keys squeezed in there and the fact that enabling num lock changes the right hand part of the alphabetical keys into a numpad, something that's really nice to have when inputting lots of numbers.
The key remappings to get a more conveniently placed right shift and longer backspace. The keys to the left of up arrow and backspace weren't used at all when using a US layout.
Manual page where they appear to brag about key switch construction. Also the top feature about how you can set the keyboard on end to save space is actually pretty convenient.
What I assume is the data sheet.