Pgs. 10 & 11 of David Markson’s copy of Scribes and Scholars: A Guide to the Transmission of Greek and Latin Literature by L. D. Reynolds & N. G. Wilson:

     On which Markson placed a check next to the information that Aristarchus “produced complete editions of both Iliad and Odyssey,” and then Markson also placed a line next to the entire paragraph where there is discussion of the marginalia signs used by Aristarchus in ancient copies of his Homeric texts.
     He then also numbered the six different signs used in the Aristarchus system:
     1) obelos – “indicated the verse was spurious”
     2) diple – “indicated any noteworthy point of language or content”
     3) dotted diple – “referred to a verse where Aristarchus differed in his text from Zenodotus”
     4) asterikos – “marked a verse incorrectly repeated in another passage”
     5) asterikos in conjunction with an obelos – “marked the interpolation of verses from another passage”
     6) antisigma – “marked passages in which the order of the lines had been disturbed”

—-

     Markson himself has six main signs he uses in the margins of the books he owned (many of which I now own) which I have gotten quite used to (yet I still don’t know exactly what they mean necessarily):
     1) checks – generally checks seem to be for anything of note (often things he then used in his tetralogy, but not always)
     2) lines – vertical lines in the margins (sometimes just one, sometimes two or more) appear to highlight major passages in a text (they usually don’t have anything to do with things that appear in his tetralogy, unless there are also checks next to them)
     3) dashes – dashes tend to be found in tables of contents next to, it seems, certain essays/chapters/stories/sections that Markson found important (or liked best)
     4) xs – xs are hard to figure out—at first I thought they might be things he disagreed with, but I no longer think that and now wonder if it is just an alternative to the check?
     5) underlines – when Markson underlines something it is usually a specific short passage in an otherwise marked up passage (with either lines, checks or xs).
     6) squiggles – a somewhat rare marking, and one that is even more enigmatic than the x.

     There are also some other random things that are much less used by Markson—sometimes brackets appear, and then there are just random markings that show up here and there.

     And, of course, the greatest marginal treats for Reader (of Markson Reading) are the notes, where he writes specific comments on the text (sometimes humorous, sometimes angry, sometimes unsure, sometimes disappointed, sometimes contrarian, etc.)…