Given the various combinations and permutations that afford greater or lesser protection from moisture and dirt –

keywind/keyset, lever set, pin set, nail set, pendant set
open face, hunting case
snap-on, hinged, screw-on covers
cuvettes
dust rings
fitch patent stems
other? –

Do watchmakers observe significant differences in protection? Is there a clear winner?

Generally, KWKS cases afford less protection from dust and moisture, primarily for one reason; each day when they're wound, a little "puff" of air enters and escapes as the case is opened and closed. Also, the key itself tends to introduce a certain measure of dust and debris, but that may or may not be significant, depending on the type of key, and how careful or careless the owner is with it.

Hunting cases typically afford less protection to dust and moisture as well, especially around the hinges, and the spring openings. As a matter of fact, in hunting cased watches that are used regularly, it isn't uncommon to find little "dust bunnies" in the space between the springs and the dust ring. Obviously, dust rings are always important and should never be left off, but for hunting cased watches, they're particularly essential.

Overall, I'd say screw back and bezel cases afford the best protection, but I've read that among the old-timers, the "swing-out" type was considered best. I suppose that makes sense, as those have half the number of joints in the outside of the case, but to my way of thinking, threaded joints that are secured tightly and are in good condition, are essentially just as good.

On a related subject, the "Oyster" case produced by Rolex, is generally considered to be the finest watch case design ever produced. As a matter of fact, it's one reason the watches are so highly regarded; the cases are so good that they keep the movements clean and dry, even under the most extreme conditions, and as an added bonus, a perfectly tight case also helps prevent evaporation of the lubricant in the movement.

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Steve Maddox
President, NAWCC Chapter #62
North Little Rock, Arkansas
IHC Charter Member 49