unknow luger

[Bakel]

Hello,

I would .like to buy a luger but i don't know what kind it is.
It is a normal lenght, but there are only a few markings:
On top is 42, on the parts is number 506.
There is also no Geschichert written at the safety pall.
It does have on the grip some attachment to put on a stock.

Does anyone know what kind of luger it is? and the value for used condition?

Thanks