Those suffixes were just designations for various revisions of the mods throughout the life cycle of the product. Sometimes it had to do with a part value revision (tighter C3 caps from the original silverface modules was an example), but most often with later PCB's. All of the PCB's were redesigned at least once for various reasons such as added features (the two switches on the 1086 being a big one), better routing of the B+ lines or better quality PCB's from a different supplier.
From a players POV, there is no difference on the XTC you have. That revision had better solder pads than the original. Some of those were impossibly small.
