That’s what Family Tree DNA now says. It’s a subtree of P312, perhaps the largest branch of R1b..
familytreeDNA hasn’t said they completed the M343 backbone testing, but the results look as if they have.
I’m looking to see if anyone else matches this, and so far, no hits.
Update 9/27/2016: working on the assumption that ftDNA has tested P311, P312, L21, Z2542 (DF13 alike), and L513, then L21 on down are all negative, and we get this positive S7123 test, derived from the Nat Geo array. It’s kind of a tree busting result.
Update 2 — Mystery Solved.
From this link, we note that the normal S7123 mutation is an Adenine to Guanine replacement. Raw data from my Nat Geo data set shows I have a Cytosine there.
So, it’s not a diagnostic S7123 change, but a random mutation that popped into the picture and causes some noise. There is a DF27 test upcoming, one ftDNA ordered and I didn’t pay for. Much appreciative of that. We’ll see what that brings. Perhaps a DF27+ and another test. At this point, it’s fair to say I’m not S7123 but P312 and need to wait a bit more.