I'll take photos next week of the dual-DSV Mark-15, all Mark-15's were set up this way by the USN for buddy-breathing.
This type of design requires a scrubber that is twice as capable as needed for one diver (duh!) as well as a large loop volume. The Mark-15 has both items well covered.
I'm just getting back into society after a 3 week diving trip, so forgive the delay in getting photos shot.
Will Smithers and I, BTW, debated and discussed the collapsed "hand-off" bailout Rebreather (Will's preference for caving) and the worn by the diver "continually managed" bailout rebreater at length some 7 years ago. He ended up playing with a hand-off rig that could be carried collapsed while cave diving and able to be passed to another diver, without much success, and my experiments in bailout systems took the other path, which I think makes more sense in open water.
I agree 100% with the concept that if you're going to carry multiple 7 litre cylinders for "bailout", plus suit infltion bottles, and all that crap, then "why bother with the loop". I'm a pure alpinist..... less crap = a lower parts count = a better chance that I'll perform perfect maintenance on all components = longer mean time between failures = higher reliability. Being a little scared all the time is not a bad thing, either....
Interesting link for those studying this:
World smallest CCR by Dave
(have a sense of humor as you read it....)
and:
Diver Dave's Minimum/Bailout Rebreather
Dave