Having fished around a little bit, it appears that, yes, Eisentraut does indeed produce brazed frames.
But I sent the seller an email last night asking for a serial number and a description of the tubing used in the bike's construction; and arose this morning to find that the auction had been closed 20 hours earlier than its listed conclusion. Struck me odd.
Nice bike, I have never seen one, but the workmanship looks excellent from the photos...The seller got cold feet because he posted no reserve pricing and no one was bidding it up. Watch for it, I'll bet he reposts it later.