CRTDI - thanks. The Firestone set was definitely an indulgence. I figured I got lucky on that one - it appears to be all there and it's in excellent condition (other than the exterior of the box.)
As for the blow-molded cases: I am certainly no fan of that style box. As you note, they waste a lot of space, and (for the most part) they don't allow the user to add anything to the set (although I noticed that S-K started making little pockets for "extras" in some of their later-production sets.) There's nothing quite like being able to "customize" your own set depending upon your own individual needs. (see photo below)
Another issue is that they're inevitably prone to failure: hinges break, latches fail.
That said, they are what they are - and most of those above are the original boxes the sets came in, so I prefer to leave them that way. Fortunately I've been able to round up dozens of metal boxes for those sets I have which are loose pieces.
hickory and Steel - interesting observation on that Truecraft driver set. Western Forge would not have occurred to me. I was quite surprised to find a U.S. made item with the Truecraft brand name on it, as my understanding previously was that all of their product line was outsourced from offshore. I don't have a Craftsman driver of that sort, so I cannot make a visual comparison. The action (as I recall) was fairly nice - as with several others above, it appears to have seen little or no use. I've grabbed it a few times recently when I got a call for some simple repair job - it was actually nice to work with.
d42jeep - thanks very much. I don't feel so bad now about my own obsession with Walden. I might have about six or eight of those 1/4" sets, but nowhere near twenty!
It must be something about the brand or the name. For reasons which defy explanation, I think I have three PM21 3/8" drive sets - the one with the wonky male-to-male "extension" that uses the female-to-female "connector".
CRTDI - as I noted above, the best box is the one in which you can add what you need to have. This old 7602 Indestro set kind of grew a life of its own over the last four decades - this is my go-to user set: