Tom, that's very interesting! I'd love to know how that would have worked, I guess it must have been rather complicated!
Si, that toolkit is for a 612. Technically it wasn't a Senior, as that name wasn't used until the 1960s - early 652s were known as the 'Hoover De Luxe', and earlier machines were simply 'The Hoover Cleaner' (as opposed to 'The Hoover Junior' etc).
Dunno if you use ebay, but there's quite a nice 612 on there at the moment, although the bag is (I think) a late 1950s replacement. Might be worth thinking about!
Si
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