Who's This? The army unit on Who's Who Vol.X's page 28.
How you could have heard of them: Uhm... Our Army at War #269 reprinted one of the stories in 1974, but the unit did not appear anywhere else before (or indeed, after) their Who's Who entry.
Example story: Our Fighting Forces #117 (Jan-Feb 1969) by Robert Kanigher and Frank Thorne (with a cover by Joe Kubert)
A touch of the strange, I said? Well, when the Hellcats climb the Alps, they find this:
Who else? While someone could make a case for the first Huntress and Hyathis to be included in this series, I think I'm going to open Vol.XI because THAT one has a LOT of characters who deserve it.