Laserjet 4Ms were incredible printers. Rock solid, reliable, cheap to run. I used to work at a place that did personalised junk mail stuff, and they'd do it by laser printing in b+w over pre-printed colour, using a giant shelf covered in Laserjet 4M+s (with ethernet cards). They could churn out hundreds of thousands of custom pages per day with that batallion of printers, and ran it all with one teenager and a cupboard full of old printers used to donate parts.

They were constructed like consumer electronics aren't any more - a thick, sturdy bent steel chassis with plastic panels over the top. You could strip the whole thing down and rebuild it without very much specialist knowledge, and parts were cheap.

I took one of those printers when I left and continued to use it for many years. The only real issue with it was it was kinda slow and a bit noisy, otherwise it was perfectly usable. Eventually got rid of it when I moved in with my partner, but my dad still has it. I bet it still works.