Erfurt Luger 1918

[weslo1969]

I have the opportunity to buy an Erfurt Luger 1918. I have been having issues trying to find values and here is why.
The pistol is not functioning and several of the parts that are supposed to move either do not or are very tight. The barrel has obvious rust in it and not sure about pitting or not didn't have the correct light to see the whole barrel. All serial number match except for the two magazines but both seem to be of german decent. The gun is currently owned by an 85 year old widow who has the p/w to show it came from the war in 1945. Also she has had it stored in a Ziploc bag in the dresser for the last 50 years so I am guessing that is where the rust is from. Also I thought that these Lugers were 9mm but in the magazine there was original or close to original ammo the read Peters .30cal or I believe 7.62mm. Is this rare or what?

Gun has heavy pitting and can not be fired in its condition. So what I am looking for is a fair value backed by someone or a book that I can share with this lady. Can anyone help? I have pics but not sure how to load them as I am brand new to this site.

Wes