zdvon, I suppose a reply this late is of little use, but, if anyone else is wondering, here's an answer to your query (which doesn't seem to have been answered exactly...).
I've recently been given a smaller, closely-related Serenelli, ostensibly a wreck, from which I hoped to salvage some parts and materials. Compared to other boxes that I've acquired, once the filth was removed, it's in surprisingly good condition, with no mould, pest attack, or corrosion whatsoever, despite its years, neglected, in a shed. I'm having difficulty deciding whether to break it for spares, or restore it. I'll ask the forum for advice, in another thread.
The keyboard in the two Serenellis is the same design. You can see what look like large-diameter washers around the pivot rod, either side of each key rod. These are, in fact, flanges on bushes which pivot on the rod, which cannot be removed. The key rods have a slot on their lower surface, open at the bottom, and are a push-fit into the space between the bush flanges. Once the key springs are unhooked from the chassis, the key can be pulled vertically upwards (at 90 degrees to the plane of the key facing). Some on my box put up a bit of a fight, but were easily pulled with parallel-jaw pliers. If you're going to apply force, try to apply it as close to the pivot axis as possible: you don't want to deform the key rod where it's weakest, over the pivot - the rod is very soft alloy. The keys are moulded plastic: it's all a bit flimsy.
Hope this helps someone. I'll post pix, if it would help anyone.
