I'll post what was once posted for me by a nice fellow on these boards over at DF (when I still visited it.)

I: The Arduin Grimoire
(1) = http://www.stud.uni-hamburg.de/users/af ... e/ag1a.jpg
(3) = http://www.stud.uni-hamburg.de/users/af ... e/ag1b.jpg
Front cover: Aerial monster, no name at foot (1), ditto with Dave Hargreave's name at foot (2), square format Greg Espinoza lizardman/saurig battle cover (dated 79?) (3)
Inside front cover: Extensive text additions relating to cover artwork, interior artwork and copyright message (3)
Title page: Scorpion-beetle critter with 1977 copyright text (1), Gryphon-type critter with 1980 artwork date.
Forward: "About three years ago fantasy roleplaying games…." With professional gamewriter spiel (TSR?) through to Eros Otus "lost and alone" pic. (1), Extensive rewrite "About one year ago, this book first saw the light of day…" through Grey Horror pic. (3)
All: pages unnumbered (1), pages numbered?? (2), pages numbered (3)
Page 10: The dread vampusa pic. (1), vampusa new pic. dated 81. (3)
Page 21: Deformed half orc pic (1), new half orc pic. with horned helmet dated 81. (3)
Page 38: A mage strikes back pic. (1), saurig pic. (3)
Page 47: Boogie man pic. (1), new boogie man pic in box dated 80. (3)
Page 53: Stalking vroat pic. (1), new Stalking vroat pic box dated 81. (3)
Page 76: Tryvern pic. (1), hobbitts vs. knoblins pic dated 80. (3)
Page 79: Otus orc & minotaur pic (1), tryvern pic dated 81. (3)
Page 86: Demon vs. rock dragon pic. (1), Storm demon vs. earth demon pic. dated 81. (3)
Page 90: The mage strikes back pic. added (3)
Maps on page 94 and inside back cover (1). Maps on pages 93 & 94; inside back cover contents index and "Fantasy Gamers" stocklist in (2); ($8.50 for I -- III, etc.) with Grimoire Games PO Box 4363 Berkeley, CA addy. (3).
Back cover: Homeward bound pic., Otus 76 (1). Square format Greg Espinoza pic., similar to cover (3).

II: Welcome to Skull Tower
Front cover: Title in outlined text (1), filled in and "By Dave Hargreave" signature added (2). (*yay for visible differences!*)
Page 40, 41/58, 59: reversed in (1), but possibly just a collation error.
Inside back cover: "This author very seriously recommends Authentic Thaumaturgy by Isaac Bonewits" (1) replaced by "Fantasy Gamers" stocklist in (2); ($9.50 for I -- III, etc.) with Grimoire Games PO Box 4363 Berkeley, CA addy.

III: The Runes of Doom
Inside front cover: Text paragraph "The imaginative and beautifully executed artwork…. Erol Otus)." added in (2).
Page 2: (1) Random encounter chart printed in error for legacy chart. Missing legacy chart printed separately and stapled in wrong place, over page 4.
Page 3: Great Orc artwork in (1), moved to page 5 in (2).
Page 14: Trelf artwork added in (2).
Page 18: Wyvergon artwork added in (2).
Page 41: Skeleton warrior artwork added in (2).
Inside Back Cover: "Fantasy Gamers" stocklist added in (2); ($9.50 for I -- III, etc.) with Grimoire Games PO Box 4363 Berkeley, CA addy.

The numbers in parentheses refer to the known print number. It does not help with the Dungeons.

I can vaguely remember some posts about the Arduin books on DF but I don't think I have ever found a good source for determining the print.

We have worked on this a bit over on the Tome of Treasures and I think at last count there were something like 11 prints of Volume 1, etc.  It seems like every copy that we end up getting is a new print.  For the original cover of Arduin Grimoire it looks like there are at least 5 prints and then with the newer cover art another 6 - with probably a few more unidentified prints out there.  Volumes 2 and 3 also have several different prints.

Here's a place to start:

Early copies were copyright Dave Hargrave so are placed here:

http://tomeoftreasures.com/forum/viewforum.php?f=266

And later prints are copyright Grimoire Games and placed here:

http://tomeoftreasures.com/forum/viewforum.php?f=129