The standard "Hostile Environment Finish" is not nearly as good as the Glock finish, for maximum durability I'd go with stainless.
I love my USP .45C, but it WILL rust on the serial#, proofmarks and any spots where the finish is thin from holster carry. If I know I'll be sweating on it alot, or out on the ocean, I'll give it a good coat of CLP before heading out.
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Cry "Havoc!" and let slip the dogs of war.