Both the factory instruction booklet and various editions of Morgan & Lester's "Leica Manual" recommend the habit of " wind, then set" for the shutter speeds.
As mentioned above, no harm will be done to the mechanism by changing speeds on an un-cocked (Leica) shutter, but there is the risk of not getting the desired setting.
There are cameras that are more fussy about this sort of thing: on the Exakta SLR's, if one is using the slow-speeds, the film must be advanced first (to wind the main shutter), then the slow speed knob must be wound, THEN the slow speed selected.
From what I've read about them, the Kodak Ektra 35mm RF had a very specific proceedure for winding & setting, which if not followed, would result in stripping of a number of delicate gears.
I think the initial warning about "wrecking the mechanism" by setting the shutter at an inappropriate time may also have come from someone more familiar with Compur-type leaf shutters from folding & press cameras: the shutter speeds in these are adjusted turning the rim of the shutter case ( on "rim-set" models), which in turn manipulates a stepped-cam inside the works, which varies the legnth of time that the clockwork escapement keeps the shutter open. In my younger ( and less-informed ) days, I would cock the shutter, then change the speed setting, and I could feel the cam "bumping" through its steps; when I would go the highest speed, it felt like a big bump.
Since then, I have learned that it is preferable to set the shutter speed first, then cock the shutter (for leaf shutters). Some discourse I have read on Rollei TLRs insists that one should NOT try to move a cocked shutter up onto the highest speed: damage WILL occur, particularly with an old, gummy shutter.
Dial-set Compurs and pneumatic "compound" shutters don't seem to be as fussy about all this.
Sorry to digress...
Luddite Frank
