@ScubadriverDale
I don’t know if Atomic submits their items for EU CE testing; and if they do, I also don’t know if they stamp the ratings on US distribution or not.
Here is a quick view of the CE current markings, which may or may not apply to your SS1, depending on when it was made and if it is stamped.
What is EN250?
In brief, on current stamps you would want to see EN250A marked, but would NOT want to see it followed by “>10°C”. I know of no such standardized rating and testing that exists in the US.
I happen to have an SS1 sitting on my desk right now that was purchased new about 6 months ago. It is marked:
CE 0299
EN 250
EN 250
From what I can find about pre EN250:2014 standards, an EN250 marking requires testing in water between 2 and 4 degrees C, suggesting that the SS1 at least is appropriate for "cold water". I can't speak for other "air 2" type devices. My guess is that some are good to go and others are not.
Of note, my Z2 first stage purchased at the same time is marked >10C on the seal that is replaced when the cold/sealing kit is installed. Obviously installing the cold kit/sealing the reg addresses this problem for diving in cold water.