Thank you Paul

sauromatian wrote in Lighter-weight, flexible but rough-covered 6th Print  DMG?:

PaulyDragon wrote in Lighter-weight, flexible but rough-covered 6th Print  DMG?:(1.) It has a rough-textured  cover, just like the first few DMG prints

What is on the bottom of the spine? An ISBN?

Yes, the same ISBN is at the bottom of the spine, without change to the ISBN code. The code is less than 1/4" from the bottom (while the ISBN on the spine of the 6th Print Gamma is noticeably further away from the bottom of the spine).

sauromatian wrote in Lighter-weight, flexible but rough-covered 6th Print  DMG?:Okay, didn't see your photo at first. The white scuffing/foxing does look very similar to the early DMGs, like my 4th print.

Another major difference: the 4th Print (which I also have) is the first printing to have the cheaper smooth cover and the last to have no ISBN, while this "6th Delta" is rough-covered (just like 1st-3rd prints and their varieties), and has the ISBN just like all of the other "Revised, December 1979" versions that began with the 5th Print.

Both "6th Delta" and the 4th Print have white endpapers and flyleaves, by the way.