Fretless wonder frets are *not* the wide and low ones used at times from the '60's through the '80's (I love those, by the way; they are on my '83 Custom, my '68 SG Standard, and my '68 ES-330). Those are huge frets by comparison.
Fretless wonder frets are even narrower than Fender wire in width. Old Fender wire is .078" wide and .040-something inch high to start. The wide, low Gibson wire is usually in the neighborhood of .095 to .105" wide (there was variation, but .100" is a good average) and .030-something inch high. Fretless wonder frets were under .070" wide, and they were dressed down to the .020's. They are so low that crowning them is pretty much impossible. Many were replaced fairly early in their lives with wider wire, either because they got divots and the frets didn't have enough meat on them to handle a fret dressing, or because players didn't like 'em. You still see them on old Gibsons, though. They even used that wire up into the '70's. (The older the LP, the more likely it is to have fretless wonder wire).
Fret wire made to the actual old fretless wonder dimensions is no longer produced. The closest you'll get is Saga Golden Gate FW-10, which is .063" wide by .028" high. It is made for fretwork on vintage folk instruments, like banjos, mandolins, etc.
Modern Gibson frets are Dunlop 6105/Jescar 55090 size (not sure which brand they actually use). They start out .090" wide by .055" tall: twice as tall as fretless wonder frets, and about 2/3 taller than the wide/low frets. These frets actually start out with a nice crown in their raw state, but Gibson flatten them during the leveling process, and heavily round the fret ends over. Then they only lightly re-crown them. Then then do only minor end dressing along the sides (something that should be done in order to blend the square corners left by the lateral roundover during leveling). This results in tall sides with a relatively square profile that easily catches the fingers, and fret ends that have inadequately softened square corners along the sides (visible in ehdwuld's and my photos earlier in the thread).
You can't dress a fret that tall as squarely as you can dress a lower fret, and still have it play ideally. Because of the height of these frets, they require a much more dramatic crown, and significantly more end dressing than lower frets, to feel smooth as can be. Again, you can play on them, and they might feel fine in the relative sense. But take them to have the fretwork finished properly, and there will be a world of difference. A thing about low frets is that the crowning and end dressing requirements are nowhere near as dramatic in order for them to feel good on the hand. Also, crappy as most people find fretless wonder frets to be for modern music, they were spec'd that way deliberately, and it took a ton of time and effort, and very precise craftsmanship to get them that way. They weren't done that way because a greedy and insane boss was breathing down their neck to bang out an unreasonable number of guitars in a day, after scaring off most of the best craftsmen in the company over a period of decades.
