I have, and have read, this Dover edition. Unfathomably, it's listed on Goodreads as being interchangeable with a modern Bärenreiter critical edition, whereas this one is a reprint of the Bach Gesellschaft (1856) edition (probably; it might even be a reprint of the first edition (Simrock) of 1845, but I'm pretty sure that like most of the Dover Bach reprints, it relies on the BGA series). Such things should be separated by content, but nothing's perfect...
Kudos to Dover for providing an inexpensive but handsome score for the Bach B Minor Mass. I once had a poster size photocopy of one of its pages hanging in my dorm room 20 years ago.