As you can see, these switches bear a striking similarity to stackpole, and that would be because they were patented by HI TEK in the 70s. There's no branding on the module unfortunately which would have been cool. Calling them lamprey switches for now on account of how they look kinda like lampreys.
this thing is clean too. unfortunately they aren't especially smooth. Not scratchy either though. they would likely take to lube well if one were so inclined.
Nickel plated
3 HTC 12? not sure what this could mean
unlike the later HI TEK and stackpole switches, these sliders are entirely in tact. I have no idea why the slider was changed for the later switches as that is a serious downgrade. These are still communal switches, but instead of a PCB they are connected by a series of ribbons. This seems to be a not uncommon trait for calculators, not entirely sure why this is the case.
as we can see here the chip is dated '74, which makes sense for this sort of machine.
and for anyone who doesn't want to click on a google link here's a mirror of the patent drawing:
