Guild has been known to veer off course at times, but the three primary colors for the X-170 have been blonde, sunburst and Tennessee orange. I have seen variations in the burst, but to my knowledge blonde was an option in each year of production. Therefore, if comparing two models of the same year B would be blonde and AB would be antique burst. If from different years B could be burst and blonde would be something else.
As for the T in X-170T, it definitely refers to tremelo. Guild produced this guitar for Mars Music in the late 90's and early 00's and utilized the Guildsby tremelo, the Guild script pickguard, and a coil tap switch. The trussrod cover, however, says X-170. I would think there is at least one non-Mars model with a factory Guildsby, but I haven't seen it.
I think volume 2 of the Guild Guitar Book needs to be released...Hans? :lol: