Hi Don
I was born in Cottage Grove and live in Springfield, between the Mac-kenzie and Willa-met rivers.
You have a very nice G date. They were made in 1935. The K dates were made in 1934. The marks are standard acceptance stamps and firing proofs. The + does indicate the spare mag. Is there a letter under the ser# on the front of the frame? Approx. 54,070 G dates were made.
A minty G date with both matching mags is worth $2000+. With holster and tool, $2500+. I'm not into Mauser lugers, so this is just an educated estimate. It could be worth more to some.
Ron