Andrej B. showed me these interesting differences between 2 copies of Advanced Dungeons & Dragons Module I3 – Pharaoh in his collection. They are different colors inside.

The modules have two cover folders with maps inside of the various adventuring locations. The interior of one folder is brown, the other blue. With these 2 modules, however, the colors are reversed.

Otherwise, they seem identical.

See also: RAVENLOFT: A look inside House of Strahd, Feast of Goblyns, The Created

PHANTOM CIRCLES: AD&D module A1 “Slave Pits of the Undercity” 1st Print

Advanced Dungeons & Dragons detailed at my reference site