I am fairly sure the Hanoverian breed stopped branding the neck in the 1990's (my 1998 mare born, inspected and branded in Germany had no neck brand.. 1992/3 gelding had one). I'm also not totally sure on this but the only horses I can remember who had the neck brand were inspected and branded in Germany..
My mare had her number on her hip, under the "H" brand and I am unsure what exactly it represents. She was eligible for the main studbook, however it was not until we took her for inspection at 7 years old that she was acctually accepted into the studbook as "Hanoverian breeding stock". It may have something to do with approval and branding as a foal and the breeder??
So all I can really guess from that is you have a horse around the age of 18-20 that may or may not be from Germany..
They say money doesn't buy happiness -- well happiness doesn't buy horses!