I'm smiling on the inside, because I'd just about bet everything Thomas insisted on the locking screw
not be located under the A string, like any other 5-string Alembic. That kinda' thing corrupted his groove. And in response, 1681 got fitted with two locking screws on its adjustable nut.
Yeah, just loosen those two inward screws first, then adjust the outer ones to set the height. Snug them back when you're done. One of the coolest basses on this crazy planet right there. It already was, then they
rebuilt it, and really went overboard.
*if you have never seen it, here's the thread on your bass,
https://club.alembic.com/index.php?topic=8344.0 it's a great look at the artistry to recreate, and the peach of a guy who had it.
There is no mention of the nut, but it appears on the last page. **read Thomas' post #39 from August 5, 2014.