Nice thread, and I'm hoping others will follow in, as there's lots of Ludwig Gurus here, and Mike Curotto is probably the best of the best. I know he's a fan of earlier Snares, but I wouldn't sell him short as an authority on this Topic.
In the 50's, like everything else American, quality was usually very good. People here took pride in thier work, and the 50's WFL Drums were very good. WFL II was just a kid back then remember.
Along came the early 60's, and perhaps drums stayed the same, but new inovations started to come to Ludwig.
I believe shell materials did change, and Ludwig (On Damen in good ole Chicago) did in many instances use what they had, tried to keep things in order with costs, and there was always the oddball one-off drum.
Brass was the norm for Hoops, Snare Shells. and of course, back in the '50's, nobody knew of Mylar Heads, as ole man Evans hadn't even dreamed of this just yet.
Note, that both 50's, and 60's Drums were of high qualty, and provided these drums weren't on the Titanic, they're still floating around today, with true, round Shells, and that's more than I can say for some modern Boutique Gretsch, and the like.
From what what I've seen personally, many of the 50's Sets had Nickel Plated Lugs, and these would dull over time. Later, Ludwig switched to Chrome Plating over Nickel/Brass. My best friend had a bought new 57 WFL Silver Sparkle Set. It vanished, being borrowed to a nephew.
Many Drums back then, particularly Snare Drums, had Heaters installed. Yes, Heaters! They threw out boxes, and boxes of these at the ole Frank's Drum Shop in Chicago. Of course, Ludwig was not the only company resorting to Heaters, when Calfskin Heads were in everyday use.
As far as sound, and value, I reckon it all comes down to condition, and originality.
As far as modern Mylar Heads go, I don't believe you'd have a problem fitting brand new Remo Ambassador, or Diplomat, etc Heads to these Drums.
I've been very impressed with remo's build quality lately, having just outfitted my entire set with Coated Ambassadors. Mark