I've been working on an 8-day clock. The dial is decently large, but the actual movement is similar to an oversized pocket watch. The only markings I've been able to find are "Sandoz" on the dial, and on the barrel bridge: An "M" with emphasized serifs "15 Fifteen Jewels", "3 Three Adjustments", and "Made in Switzerland" The serial number 403250 While working on it, the click spring went *ping* into oblivion, and despite my best efforts and strongest magnets, I haven't been able to find it again. At this point, I'm looking to replace it. However, just going off the above markings, I haven't been able to find any information about the movement classification or caliber in order to find a proper replacement. Since it's a click spring, I'm not too concerned about getting an exact replacement just so long as it applies pressure to the click. The original was just a simple spring consisting of a single U-bend and fit into a channel 8.4mm long, 2.9mm wide, and 0.54mm deep. How would I go about finding more information on this movement in order to get a proper spring? Or just search for springs that have the right shape and dimensions?

Yes it can;  perhaps impulse jewel can't enter the fork horn, if the shock has  knocked a pallet jewel out of alighnment or bent a pivot. Remove the two black screws then the automatic device, loosen the cock screw by couple turns, raise the bridge just enough to pass the impulse jewel over the fork so to get impulse jewel inside the horn, tighten cock screw. It will run, however , might get stuck again if pallet jewels have got misaligned or a pivot has got bent.

A little uninspiring.  It does run though...kinda.

I decided to find a knew winding pinion for my Vulcain.  I see some wear on the one I have.  I have the spec sheet on the Vulcain 120 and identified the part as #1246.  I searched around and found scotchwatch.com had one.  $45.  I really want it, so I bought it.  Meanwhile, I continued my search and found a part with a different part number (410) on Northern Watch & Clock Supplies in the UK.  It was just a couple of pounds, so I bought it. Later I looked at the invoice from scotchwatch.com and see that the part I bought is 1246 (410), so I think the part has two numbers.  Well, we will see when they arrive.  On part cost 20x the other one.  I am not complaining...as I am glad that someone takes the effort to maintain an inventory for budding watchmakers like myself.  I just think it is interesting. Learning new things every day.

Thank you for your introduction and welcome to this friendly forum. A nice looking watch you are wearing.