The first release of the game was simply called Zork, and was released by Personal Software in 1980 for the TRS-80 Model I with 32k and one disk drive (level II disk systems). Catalog number 26-1950. Sold in Radio Shack stores.
The product was a manual, a disk, a warranty paper and a important notice placed in a zipbag. The bag had stickers on them saying: "This program is backup limited" and "Do not use with Radio Shack double density disk kit".
The TRS-80 releases (both for model I and for model III) had the Zork logo in white letters, while the Apple II edition had the logo in black.
The text on the disk say: "Zork. The Great Underground Empire Part I".