NN was formerly part of the German Empire. In the German Empire, the place was called NN.
The place is now called Háj u Duchcova and belongs to Czech Republic.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| NN (Háj u Duchcova) | Austro-Hungary | Dux | before the Treaty of Saint-Germain |
| NN | Czechoslovakia | Duchcov | after the Treaty of Saint-Germain |
| NN | German Empire | Dux | 1938 |
| Háj u Duchcova | Czechoslovakia | Duchcov | 1945 |
| Háj u Duchcova | Czechoslovakia | Teplice | 1992 |
| Háj u Duchcova | Czech Republic | Teplice | 1993 |