You know, now that I'm thinking about it, I collect DM screens as well.
Not so long ago I was pondering how many D&D screens there have been over the years. The answer turned out to be 38 (with two more on the way), assuming that I didn't miss any...
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Dungeons & Dragons screen checklist
Dungeons & Dragons
Judge's Shield (1977) [JG28]
AC2: Combat Shield and Mini-Adventure (1984) [TSR9099]
AC7: Master Player Screen (1985) [TSR9156]
Dungeon Master's Screen (and folder) (1991) [included with The New Easy to Master Dungeons & Dragons Game, TSR1070]
DMR1: Dungeon Master Screen (1993) [TSR9437]
Dungeon Master Screen (1994) [included with The Classic Dungeons & Dragons Game, TSR1106]
Dungeon Master Screen (Two-panel) (1999) [included with Dungeons & Dragons Adventure Game, TSR11450]
D&D Diablo II DM Screen (1999) [included with D&D Adventure Game: Diablo II Edition, TSR11548]
Advanced Dungeons & Dragons
Dungeon Master's Screen (1979) [TSR9024]
REF1: Dungeon Master's Screen (1985) [TSR9146]
Advanced Dungeons & Dragons 2nd Edition
REF1: Dungeon Master's Screen (1989) [TSR9263]
Ravenloft Screen (1990) [cover of Feast of Goblyns, TSR9298]
SJR3: Spelljammer Dungeon Master's Screen (1991) [TSR9313]
Dragonlance Dungeon Master Screen (1992) [included with Tales of the Lance, TSR1074]
Al-Qadim Screen (1992) [included with ALQ1: Golden Voyages, TSR9366]
Fighter's Screen (1994) [TSR9457]
Priest's Screen (1994) [TSR9462]
Thief's Screen (1994) [TSR9463]
Wizard's Screen (1994) [TSR9468]
Planescape Dungeon Master Screen (1994) [included with the Planescape Campaign Setting, TSR2600]
First Quest Dungeon Master Screen (1994) [included with First Quest: The Introduction to Role-Playing Games, TSR1105]
Ravenloft Dungeon Master Screen (1994) [included with Ravenloft Campaign Setting, TSR1108]
Masque of the Red Death And Other Tales DM Screen (1994) [included in the Masque of the Red Death,TSR 1103]
Birthright Dungeon Master Screen (1995) [included with the Birthright Campaign Setting, TSR3100]
Dungeon Master Screen & Master Index (1995) [TSR9504]
Introduction to AD&D Dungeon Master Screen (1995) [included with Introduction to AD&D, TSR1134]
Dungeon Master Screen (1995) [included with The Complete Starter Set: AD&D Game, TSR1167]
Dark Sun Dungeon Master Screen (1995) [included with the Dark Sun Campaign Setting Expanded and Revised, TSR2438]
Dungeons & Dragons 3.0
Dungeon Master Screen (2000) [WOC11639]
Ravenloft Secrets of the Dread Realms and Dungeon Master's Screen (2001) [WW15001]
Forgotten Realms Dungeon Master's Screen (2002) [WOC886860000]
Kingdoms of Kalamar Dungeon Master's Shield (2002) [K&C1006]
Dungeons & Dragons 3.5
Dungeon Master's Screen (2003) [included with Dragon #310, PZO82310]
Deluxe Dungeon Master's Screen (2004) [WOC885960000]
Kingdoms of Kalamar Dungeon Master's Shield (2004) [K&C1023]
Dragonlance Dungeon Master's Screen (2004) [SVP4901]
Eberron Deluxe Dungeon Master's Screen (2005) [WOC950060000]
Dungeons & Dragons 4th Edition
Dungeon Master's Screen (2008) [WOC218307400]
Dungeon Master's Screen (2010) [included with the Dungeon Master's Kit, WOC244640000]
Deluxe Dungeon Master's Screen (2011) [WOC280590000][/size]