I would assume that the clock on Bilbo's mantelpiece (
The Hobbit, Chapter 2) is mechanical. As a matter of fact, I incorporated several ideas that you mention,
Legate, into a fan fiction* about Hobbits who stayed in the Shire during the War of the Ring! I too assumed that clocks were a Dwarven invention and that any knowledge about their workings came to the Hobbits from them.
*
Folco's fan fiction story - still incomplete, but not entirely without hope...
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'Mercy!' cried Gandalf. 'If the giving of information is to be the cure of your inquisitiveness, I shall spend all the rest of my days in answering you. What more do you want to know?' 'The whole history of Middle-earth..
.'