I just got back from my FFL where I had a chance to really examine the barrel proofs. Because it has been buffed and reblued it is really hard to make out the proofs. I did get some more photos and, using photos of one of Don's Lugers, I have put together a comparitve analysis below.
Left Side Barrel Proofs:
Here we see a comparison. The top proof does look like it could be an E/36. The middle proof could be the top of the wings of the larger Eagle but what's below it is questionable.
Right Side Barrel Proof:
In this comparison you can definately see the faint traces of a proof there. It is in the correct location. It is possible that it is a PTV/E.
I did not get a photo of it but also stamped inside the frame but not on the lug is this same "oval N" as shown in Don's photo below. What was this proof?
I also want to note that, although the barrel/receiver has been reblued, the front of the barrel is worn to a very shinny metal. As if the tip of the barrel had been rubbing it's nose inside a holster for some time. Another mystery as if the barrel/receiver had been recently reblued as part of a restoration project, why would the barrel front be worn as if it had lived in a holster for a long time?
It's unfortunate that the barrel/reciever has been buffed and reblued which has caused the proofs to be so unreadable. I do believe that there is enough evidence to at least give some possibility that the barrel/reciever is a 1929 rework. We see that the barrel has been stamped with matching numbers to the reciever, the receiver is dated 1917 and has the "sight notch" of previously being a LP08, and it has been fitted with a safety sear. This along with the proofs that are there does point it to possibly being a 1929 rework.
I hope this additional info can help to get us a little closer to the truth.
Thanks again!