Follow-up; the plot thickens! Now that I've removed the keycaps to send back to the original owner (like I said), I discovered a few weird things.
1) The plate has holes for Alps stabilisers, but the keycaps have Cherry stabiliser mounts. The keyboard doesn't actually use any of the stabiliser holes except for enter and space.
2) The enter key uses both rod and wire stabilisers.
3) The enter key uses a genuine white Alps switch of a fairly early make; it's one with a blue top housing and long white switchplate (but it does have a logo). When testing the bare switches next to each other, the Alps switch feels heavier than the Aruz ones.
Here's the board with the Focus set on it, as I said I would. As you can see it fits it pretty well, and the board now has the strange distinction of being better stabilised than it was originally as I have fully compatible stabilisers for it xD . I think it looks pretty good this way!