Hi Pepe
Simpson Ltd has a couple of of similar guns on their web site.
They are high in their prices, but give you an
idea of what the high price might be.
I have seen these go for about $1500, here in the states.
Otto may be correct for his area
http://www.simpsonltd.com
Look carefully for mixed parts, very common on Portuguese Lugers as they stayed in service for so long. Look at the grips of the gun in question, they look a little to good to be original, untouched. Also the safety marking does not appear to have any white left, may not be a concern but often removed during refinishing.
Good luck!
Vern