The Series I had done text, if you wanted 12pt Courier, and 150 dpi graphics. It cost a couple of thousand pounds. (Or was it five?) The actual engine was bought in from Canon, with a deal that forbade Canon from using the 'Printer Control Language' that HP designed in their own printers.
In the days when each program had to be told what sort of printer you had and how to talk to it, this doomed Canon's own printers to relative failure. Almost everyone else used PostScript (and cost an absolute fortune, memory is telling me than when HP's cost 'only' two thousand, any thing with PostScript was at least three thousand and was considered 'cheap' at that price) or emulated PCL.
The Series II increased the graphics resolution to 300 dpi (mind you, you couldn't do a full page of graphics without expanding the memory - add at least another five hundred pounds) and brought us soft fonts: you could download any font to the printer, if you knew what it looked like.
You know that the internet was designed to survive a nuclear war, well, I sometimes think that the LJ II was too. It was from a time when HP was run by engineers and, as I've been reminded today, it weighs 60lbs. If they didn't sell millions of them, they must have come close. The number of pages printed by them must be in the hundreds of billions, as they go on working forever (see the comment about being run by engineers!) and it's very common to find one that's printed well over 100,000 pages.
Its mammoth success meant a huge range of third party products appeared. These were encouraged by the expansion slots HP built-in: two in the front and another couple round the back.
The former were used by were dozens of font cards, to expand the number of fonts without bothering with soft fonts. Even Microsoft did one (font cartridge 'Z').
But the real gold was in the other slots. You could do virtually anything with the right card.
So, for example, somewhere I have a card which talks to the PC via a cable and which drives the laser engine directly. This increases the resolution (something HP were later to do with the Series III) and makes it faster. Say you've got a page of graphics. Instead of having to send about 1M of data down a relatively slow parallel port for the printer's internal CPU to sort out, your fast PC can work out what goes where quicker and squirt the data down a fast link. The actual page appeared at about the same speed as a page of Courier and you could get eight (different) pages a minute. Oh, no need to expand the printer's memory either.
Another card used a similar idea to give you genuine Adobe PostScript: it had the 68000 CPU and 3M RAM of the Apple laser printer - both HP and Apple used the same Canon mechanism - for a fraction of the cost of the Apple product. (Owners of the first Macs may remember that their printer had a faster 68000 and more RAM than their Macs!)
Plus there were at least ten PostScript emulators out there.
More boring - for me anyway - were network adaptors or cards that let you plug in several PCs to the same printer, handling the print queue. (Remember, at the time, a printer like this would cost as much as the PC.)
The card I use now is a combination accelerator (with its own CPU), RAM expansion and PostScript emulator. Ghod knows what it cost new. Hundreds, certainly. I found it for a fiver in a charity shop.
I wasn't surprised. For some reason, you have difficulty giving Series II or III printers away.
Yep, they're heavy. Yep, they don't do colour. Yep, it's "only" 8 pages a minute (but for home use, how many do you need?) Yep, it's only 300 dpi, but for text you've got to look really hard to see the difference.
I've got two, plus the Series III that's actually used now and replaced one of the IIs. The III, as mentioned earlier, increased the resolution a bit and also added scalable fonts. Yep, you could tell the printer 'I want 13.5 pt Univers' and it'd do it without messing around with soft fonts or spending money on another font cartridge.
If you see one, and you've got the space, get it. None of mine cost more than £20 and they'll probably be working long after you've stopped. This one has survived four PCs of mine and doubtless a few more with its previous owner(s).
(Oh, when HP stopped making toner cartridges for the Series I a few years ago, they gave anyone who still had one a new printer... Mind you, it was one of the post watershed ones, ie after the Series 4, the last one before the marketing people took over. I expect they'll be making cartridges for the II & III for decades, but you never know.)
So you can imagine my horror when the Series III stopped working just before the latest building work started. It wouldn't accept there was any A4 in the paper tray. Eeek.
Today, I move it to its new home, with the PC under the stairs, and open it up. Turns out that a polystyrene nugget from when it was shipped to me has been living in the far rear of the paper slot for the past eight-ish years. A bit broke off and stopped the switches that determine which size paper you've got from closing properly.
I think it's the first real problem I think I've had with it in that time.