Remember to back up your save game files before doing any of this!
To duplicate item just follow the step below:
First, Drop the item you want to duplicate on the ground, then save the game in slot 1.
Second, Pick the item that you drop and save the game in slot 2.
Third, Alt-Tab the game and open the explorer, copy the file name "player_01.gam" (default: C:Program FilesGMX MediaSeal of EvilSystemGame) into a new folder.
Fourth, Rename the "player_01.gam" as "player_02.gam" and copy the new renamed files into the game directory.
Finaly, Load the slot 2 save game.
Have Fun by Lantz Kirby