I made it up into the attic a few weeks ago, and there are, indeed, three 91xxs in there. One of them seems to have some broken bits to the casing as the side panel doesn't want to stay on properly. Admittedly, it's a bit awkward to assemble/disassemble that kind of them in the attic but the bits that fell off are a clue.

Anyway, one of these days I'll mess with them. I'm just falling further and further behind on projects and thinking of new ones to add to the list...

Part of the problem is that i have some real-time hobbies like gardening and fish keeping and when weeding needs doing, or water changes, you really can't put them at a lower priority than other projects. It must be done when it needs doing. The eight-year-old boy runs in real time too.