Both of these were pseudonymous, of course--yet not of the common Anson MacDonald byline most of us are familiar with as Heinlein's second-tier name of the early 1940s. No, "Beyond Doubt" is a Lyle Monroe--a name Heinlein used on only three other stories, it seems--and "They Do It with Mirrors" is by Simon York, a name I don't think he used anywhere else.
Now, "They Do It with Mirrors" was reprinted in the 1980 Expanded Universe, so although I haven't read story in close to 40 years, when I want a reread, I'll probably do so in that newer book. "Beyond Doubt," though, has never been reprinted, except, I suppose, in the big leather-bound, acid-free, limited-run 46-volume Virginia Edition. I guess I could read it in the Virginia Edition, but the Astonishing Stories was in pretty decent condition for an 80-year-old pulp magazine, so I simply read it there with some care. Very satisfying like that. And that's how, come to think of it, many months earlier still, I did with the elusive "My Object All Sublime" in the February 1942 Future Combined with Science Fiction.
In any event, these recent funky finds now are photographed, and posted to the "Pulp Magazines" page of my "Heinlein Cover Art" galleries. Oh-- And in the pic here, by the way, note that this interior art is by the famed Hannes Bok.