Hammer was formerly part of the German Empire. In the German Empire, the place was called Hammer.
The place is now called Hamr na Jezeře and belongs to Czech Republic.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Hammer | Austro-Hungary | Böhmisch-Leipa | before the Treaty of Saint-Germain |
| Hamr | Austro-Hungary | Böhmisch-Leipa | before the Treaty of Saint-Germain |
| Hamr | Czechoslovakia | Česká Lípa | after the Treaty of Saint-Germain |
| Hammer | Czechoslovakia | Česká Lípa | after the Treaty of Saint-Germain |
| Hammer | German Empire | Deutsch Gabel | 1938 |
| Hamr | Czechoslovakia | Česká Lípa | 1945 |
| Hamr na Jezeře | Czechoslovakia | Česká Lípa | 1992 |
| Hamr na Jezeře | Czech Republic | Česká Lípa | 1993 |