You have a rifle made of fluid steel from the Krupp steelmaker at Essen Germany. That is as much information as we can give you from the information you gave us. A gunsmith should be able to identify your gun in person, but we would need a lot more information to make a good guess- sorry.
Take it to a gunsmith.
No published sn data
No sn data available.
Brno is in Czechoslovakia, Essen is a city in Germany. Two different countries. "fluss stahl" refers to "fluid steel" made by KRUPP Industries located in Essen, Germany. Since Krupp was one of the premier manufacturers of high quality steel products in Germany prior to (as well as after) WW2, there is a good chance that Brno used KRUPP steel to produce rifle barrels. Especially in the late 1930s.
A type of rifle made in europe.
Unfortunately, there was more than one company that used the Essex name, The "Krupp" marking was the German steel firm that produced the fluid Steel (Fluss Stahl) used to build the rifle.
No published history
Have it checked over by a gun smith.
Read the roll mark on the rifle.
The Paris gun of WWI. It weighed 256 tons. it was 28m long and fired a 240mm round. It was made by Krupp of Germany. The German army used it on Paris France.
3 barrel guns (most commonly 2 shotgun and one rifle) are known as Drillings, from the German word for 3. Suhl was the city in Germany where this gun was made. Krupp Stahl means steel made by the Krupp company of Germany. If you do a Google IMAGE search for German drilling gun you will find several pictures.
First, you'd need to know what type of rifle it is. There's plenty of resources available online which can identify markings and such, but they tend to be oriented towards one particular type of rifle.