I’m not very adept with a pair of calipers. Today I tried to measure the frets on all the guitars I have in the house (snow day with nothing much to do). I know approximately how big the frets are supposed to be but for some reason my measurements aren’t that close. Of course, the size of the fret wire as it came out of the box 50 years ago (or tube or whatever) isn’t necessarily the size of the fret wire today. Some general knowledge of Gibson’s fret “repertoire” will help. In 1958, Gibson wasn’t using what we now call “jumbo” fret wire in the first 335’s off the line. The first thing I noticed when I picked up the first 58 I ever owned was that the frets looked like vintage Fender frets (I was a Fender guy before I was a Gibson guy). I measured them at .075″ which is pretty close to Fender which, if what I read on the internet is correct, are .078″. Often, when I get a request from a potential buyer for a dot neck, I ask whether they want a 58, 59, 60 or 61. Most want a 59 and when I ask why, they sometimes say “I can’t play on those little frets on the 58″. I’ve been playing a string of 58’s for the past few months and, while I’m not the world’s best player (OK, not even a good player), I find very little difference between the feel of a 58 and the feel of a 59. Big bends seem to work just fine on the “little” 58 frets. I think setup has more to do with bending than fret wire does but perhaps fat frets are more forgiving of a mediocre setup. I’ll have to look into that. I measured a few others as well. The frets on my 59 ES-345 were around .085″ and were extremely comfortable -a bit flatter than the 58’s but that could be from dressing and wear. The 66 I have had about the same size as the 59 only taller. I have an 82 here that measures .092″ so apparently bigger frets were introduced at some point after the 60’s ended. My 59 Epi Sheraton’s frets measured .080 but I’m such a klutz, they were probably the same as those on my 59 ES-345 and I just didn’t a good measurement. These are pretty small differences after all. But, when you compare these “vintage jumbo” frets to modern jumbo frets, they are quite a lot smaller. A .085 today is considered medium. So, what do I specify when I need to have one of my vintage beauties refretted? I’ve had great results with Dunlop 6105 wire (.090″). It’s so close to vintage spec that I can’t tell the difference. I played refrets done with 6100, 6120, Stew Mac 146 and 154 and they all seem pretty good. I will say that I’m completely obsessive about proper intonation and the big wide 6120’s make intonation more difficult and finicky-especially when they need a crown. In fact, all these frets, once they flatten out from wear (“railroad ties” in luthier vernacular) will cause you some intonation issues. It’s simple physics really. The more precise the pressure point on the string (i.e. the top of the fret) the more precise the note. With flat frets, if the string contacts the back edge of the fret, the note will be rather different from the note produced at the middle or front edge of the fret. On a properly crowned fret, there is only a single point at which the string touches the fret. That doesn’t mean you can get away with poor intonation but it allows you to better adjust and control it. So, I’m afraid I haven’t shed that much light on which 335s used which frets-it seems like 58’s used little ones and 59-66 (and later) used what would be called medium today. If anybody is real good with the calipers, I’d be happy to learn what you find. 99% of what I know about these guitars comes from owning them and looking at them. You can’t get most of this stuff from a book.