Continuing with the top assembly of the Standard Folding typewriter; the carriage was taken off (is was barely hanging on anyways, with only one bracket left). Then first the carriage base-assembly with the folding-arms was taken apart. End result is a pretty bare baseplate and lots of grimy bits grouped in bags. Only the escapement rack and the rear guide-rail were left in-place.
The baseplate is a fairly basic 'slab' of aluminum, also with the dull, passivated finish. The normal cleaning with soapy-water and vigorous scrubbing would have damaged this finish. As an alternative, the part was washed in acetone, 'scrubbing' gently with a soft toothbrush. (Outside/well ventilated and gloves.)
Bag-by-bag all the groups of parts were cleaned with the usual techniques. The spool-bases had originally been blackened and by now become rusty. These were sanded smooth to the bare metal and painted with a satin-black finish.
Result then; a nicely clean baseplate and a collection of clean sub-assemblies. As stated in service-manuals of the time, assembly is the reverse of disassembly.
One unexpected complication was the worm of the right ribbon-feed. This was broken! Somehow it got a knock that spread the worm-thread wider in one spot. This made it jam on the sprocket of the spool capstan; it cannot have worked after that damage. Weird that it even broke the worm where it is fixed with a pin to its axle, but did not destroy the flimsy spool-base. Must have been a very targeted knock.
Fortunately it could be tweaked back into functional shape - well, bent-with-brute-force really and some filing too. The broken and bent-back two parts of the worm were locked on the axle with cyanoacrylate. (In case the worm would've completely disintegrated, a new worm would have had to be made - could probably have been done; tin-plated copper fuse-wire is soft and available in suitable gauge.)