Daniel,
At the risk of looking a gifthorse in the mouth....
One perennial problem of these kinds of competition is that some of the scopes end up being resold pretty quickly; OK, so that gets them out, eventually, to people who can actually make use of them, but its frustrating to the rest of us and, quite frankly, doesn't do a great job of market intelligence collection either, which is presumably one of the reasons you do this....it also means you've lost a potential commercial sale when a 'real' customer finds a bargain offer on eBay or whatever.
So, how about a selection option for what 'class' of scope you'd like to be in the draw for?
That reduces the chance of someone winning a scope that's either hugely above or below their use level, which would hopefully reduce the chance of them wanting to resell it. You're going to have more low end scopes than high end ones, so provided punters are only allowed to enter for one 'class' or the other then they would self select according to their need.
Personally, I'd be happy with a smaller chance of winning a MSOX4104A than a bigger chance of getting something that wouldn't be a step up for me and would deprive someone else of the chance of getting a step on the ladder.
DAVE