Found this one in Spain’s Guardia Civil website:
Tried to look for more info about it but other than identifying it as a PD model manufactured in the 1930s, there was nothing out there. the magazine appears to have a 32 round capacity which makes me think it was a 9mm (either 9×19 or 9×21) and in the tradition of the Luger, you could store the gun inside the stock. Where you could store the magazine? No idea.