The manual mentions a bonus scenario for successful registration of the game on page 3. The files were in the CD's /.iso's REGDATA folder and need to be copied into the scenario folder. Then the scenario will be available in-game.

GOG, can you add this be default?

Peach Mountain also has the scenario 'The Highway at Volokolamsk' for download and mentions it has been created by the game developer, SSI. The file modification timestamps are early and support this argument. Maybe this scenario got used for testing because there are only 3 units already in one's forces and enough prestige to buy many more?

Trivia: The Volokolamsk highway was the final scenario of the Eastern front in Panzer General 2.