What an honor! a Leica M5!The long exposures timer is seized up.Unfortunately, the owner did not give the lens, I would have made a test film!
The removal of the top cover is not a big problem, except for the cocking lever that requires a special tool, fortunately available on the internet (ebay!), and which I'll have to wait for before operating. The upper strap hook must also be removed, the screws cover fall apart when you try to remove it, but my client knows it and takes care of its replacement (already missing on the bottom hook).
Here is the cover removed. Disassembly will stop here, the long exposures timer is on the same location as on a Zorki (how curious!), but with much more "crowd" around. Only will be necessary a few drops of my cleaning product (using a syringe) in the right place, and to make this timer "work". Go!