Here's one that will never 'Need Tuning'.
The Dulcitone is older than I thought - it was invented by Thomas Machel in Glasgow in the 1860s, around the same time that Mustel invented the Celesta. Not sure when this one was made - possibly in the 1930s?
The tone is produced by felt hammers (just like a piano) striking tuning-forks.
Dulcitones do come up for sale occasionally, but it is rare to find one that works properly. The owner has made the following recording:
Please listen to this anyway! If you notice a bit of a squeak (you will now that I've mentioned it) this is the pedal-link, which has now been silenced.