Look at what I found at a yard sale today.
I thought the two Dungeon Masters Guides were identical at first, but as you can probably see in the first picture, there's a slight differences with the covers, mostly with the TSR's logos and name - the first copy has TSR Games, while the second has TSR Hobbies, Inc. I have no idea when the guides and handbook were printed other than 1979-1981. They're definitely for 1E AD&D.
I'm considering doing a contest in the future with one of the guides as the prize.
I would've failed my saving throw if that guy had had the Monster Manual too.