No expert here either. The details and differences of Gibson's slope dreads can be confusing even to those of us who are big fans. Gibson has made so many variations of it's basic designs over the years, and continues to do so, that it can get hard to keep up. Throw in the Custom Shop varieties with different woods, etc, and, and no wonder your confused. Here's what little I know, hopefully someone more knowledgeable will show up and fill in some information.
Keep in mind that there are significant differences between a J-45 and an AJ. The AJ has rosewood b/s, a long scale, and very different (forward shifted, if I'm not mistaken) bracing. The J-45 is short scale with mahogany b/s. Basically very different guitars.
1. This isn't a J-45 at all, but an Original Jumbo, purportedly based on Gibson's "Jumbo" from the 1930's. The Jumbo predated the J-45 by several years (Gibson simply called it the "Jumbo" at the time of its introduction and it's where the term originated, as far as guitars go). Whether the current OJ is true to the original in terms of bracing, etc., or a more modern design masquarading as the original, I have no clue. I've never played one, but the reports I've read from folks more experienced than I is that tonally it falls somewhere between the woody sweetness of the J-45 and the in your face volume of the Advanced Jumbo.
2. As mentioned by Woodruff, the Southern Jumbo is simply a J-45 in fancier appointments. The 1942 Legend series J-45 is a recreation of an actual 1942 (the year it was introduced) J-45, using the same construction methods, woods, bracing, etc. All handmade, reports are that it's as close to a vintage J-45 as your ever going to get in a modern guitar.
The TV, or True Vintag, series, by the way, are guitars that use the AJ style of bracing. Most, but not all of the J-45 TV's I've played have been quite a bit better sounding than the Modern Classic (MC) versions (the current standard version) J-45's. There are TV versions of the J-45, J-200, and a few others, none of which used this style of bracing on the originals.
3. This is a totally custom guitar. True enough it has (like the TV's) AJ style bracing, but it's not an AJ. Remember, the primary differences between the AJ and J-45 are scale length, bracing, and woods. So, this will be a short scale custom J-45 with fancy wood combo.
And you thought you were confused before
