During and after World War II, various technical and scientific intelligence agencies and groups of the United States, Great Britain, Soviet Union, France, and other allied countries diligently searched for any and all advanced German technolology. This included the search for develped technology, as well as, techonology that was just in the conception and design stages and had not yet been produced. These activities included the confiscation of the German Patent Office files, including German patents that had been issued, but also German patent applications.
The reason for all of this was that the US realized that it was substantially behind the Germans in several important technological areas such as rocketry, aircraft, metallurgy, and a number of other areas.
It is highly probable that the current German Patent Office has gone back and reconstructed the patent numbers and the patents that were issued prior to and during WWII. And they may have an online, searchable database, just like the US has. So it may only be necessary to identify the website of the German Patent Office to get access to issued German Patents.
References and further information:
1. Official German Patent Office Website: http://www.dpma.de/
2. Wikipedia page about the German Patent Office and history of that office:
http://en.wikipedia.org/wiki/Deutsches_Patent-_und_Markenamt