I enjoyed that. Imagine one of your wheels is a bit 'out' regarding phasing for the coupling rod re-installation. At best (it's out on both wheels on the axle by the same amount) you somehow have to twiddle that axle around a bit while all the others stay put (chock everything, use a strop around the wheel spokes, pull with crane, break something?). At worst, your wheels are out of phase on one axle, and you are presumably screwed! BIG heavy stuff, very accurate, out in the ****ty grimy world getting worn out really quick! Nice to see young blokes involved - at our engine museum I (55 y.o.) am youngest by a long way. And on that subject, I didn't even look at the watch stuff, it would get me down too much. My eyes are poor - two pairs of glasses needed for detail things, and that gives such crap depth of field (and my memory of putting things down is so poor) that I spent more time groping around the bench searching for things than I do working. Teeny tiny stuff is not for me - I don't want to get much smaller than a pivot screw.
Back on with my Martin musings - we seemed to have pinned it down to a 1927 HC stencil, but have a look at this. I thought at first the odd-looking B-Bb roller was an add-on commissioned by some owner who liked to move that way, but I have seen pics of another 'Lewin' stencil alto which is just the same. And the table does not look much like a '27 HC, or (from my position of relative ignorance) very much like other, later, Martin efforts either, where I think C# comes down and allows horizontal movement straight onto Bb. Rather odd.
(Edit - a hypothesis occurs to me. I wonder if they bought older horns cheap (1927 pattern, say) - but specified the current-line Bb key (because it would fit and they thought it made a big difference to playability). But maybe the 'new' C# key wouldn't go on the older-style horn (which has a one-piece C#), which is perhaps why that flat top (in my side-on pic) of the Bb key which looks like it should adjoin something, doesn't - and maybe they added that strange little tapered roller as an attempt to make getting from C# to Bb more do-able in the circumstances? If that holds up, dating the horn on the Bb key would make some sense!)
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