PWM
as rigbymauser stated, you could not compare a Krieghoff double with a Holland & Holland double!
One the other hand the price for the 500 on ebay seems way to high, I thought that also when I have seen that gun weeks ago.
During a visit to Hartmann & Weiss, a couple of monthes ago, I had the opportunity to see and handle the .600 NE H&H double, which at one time belong to his Royal Highness Maharaja of REWA. Build in the 1920's in only, if I recall it correctly, 12 weeks during a visit to the british King the rifle is equiped with a foldable, diamond moon front sight. Fully cased this gun costed originaly 120 pounds ( there is a rumor that his Royal Highness has forgotten to pay the bill, and the britsh King has overtaken it quietly!!!

)
Beside all the story, the requested price for this 600 Nitro which was on sale, was 110.000 Euro. I would rather buy this than a .500 with unknown history for 150.000 Euro

Robert