I'm sorry, but although this will be of no use to you, I still have to chime in.
You have come up with a portmanteau of model names. The Balanced Adjustable was called the 150. The 109 was adjustable but non-balanced. And the graphite non-balanced modern regs are the only ones to carry the R- designation (R-190, R-380...).
The Regulators
Scubapro names it's regs using a letter to denote the designer. In that regard "R", "D", "M", "G", "S", "X", "A" and now "C" all reflect the name of the primary designer involved with the second stage.
I am not sure who designed the "108" High Performance and "109" Adjustable, but the use of the "R" with those designs has become common place.
To get picky, the schematic for the "108" High Performance second stage is titled "08X" not 108, but a few of the parts, such as the poppet stem, are "108" numbered, and to make it even more confusing the adjustable orifice demand valve body (a key feature of the High Performance versus the early unbalanced second stage) is a "190" part number, and suggests the hand of the R190 engineer in at least the revision of the "High Performance"/"108" design.
Personally, I think the original Buechat unbalanced second stage was the "080" and the later revisions with key "108" parts led to the "108" designation.
The Balanced Adjustable was the 15X with the "X" being the number of revisions to the design and as far as I know there were 6 major revisions of the design. However the last 109/15X schematic for it is "r", suggesting numerous revisions to the original 109 design.
So, it's now my practice to only visit once a day while not logged on and read through the only forums worth reading (vintage and tanks), then keep track of which threads I may want to post on so I can go directly to them after I log on so as to waste as little of my time as necessary. The admin had the audacity to suggest I change my end of things, when this is the only slow site I visit on a regular basis. All the other sites are up to speed, but not this one.
