I know what you mean on getting two people that want it in a bidding war haha. For a very long time, I had been looking for an m13 spam can of grenade cartridges that had the m3s, the m6s and the M7 booster cartridges(A little bit of everything). Well finally one showed up on gun broker and I got into a bidding war with another guy and I ended up paying $850 for it haha. Of course I way overpaid for it but they come along so very rarely, me and my son had already decided it was coming home to our collection before the auction had even ended regardless of what it was going to go for. Depends on how bad people want it. If things like this 20 mm anti-aircraft shell is very rare in your neck of the woods, I could easily see it reaching your estimate and then some