From the Introduction:
The world of Steam & Rust is a steampunk fantasy setting involving the inter-dimensional collision of a world similar to our own at the start of the 20th century - the world of Steam - and a world rife with entropy and decay - the world of Rust.
Players take the roles of archeologists, explorers, treasure hunters, scientist–inventors, military men, spies, or similar adventurous characters from the world of Steam. (The world of Rust remains largely unknown and unexplored at this point.) Because the world is a very wide place, this setting chapter focuses on Russia.
Step into a world that smells of oil and wood smoke, of gunpowder and ozone, of lush forests and unspoiled seas, of fresh-baked goods and drying herbs. It's a world filled with locomotives and airships, with spies and military conquest, with exploration and adventure!