Wow, three H&H 8bores on offer at the same time!
This is a good opportunity to do an impromtu study of these guns.
I notice the one at Champlins looks like it has flat sided hammers and sideclips, but is an earlier gun than at least one of the others.
Interestingly, the damascus is different on all three. In fact, two have the steel wrapped in different directions on the right barrel - one clockwise, one counter clockwise. I wonder which way the rifling turns...
For aesthetics, the steel was wrapped in opposite directions for each barrel, but I am not sure if the barrels were rifled in opposite directions as in some doubles.

http://www.gunsinternational.com/HOLLAND...un_id=100083742

http://www.gunsinternational.com/H&H...un_id=100071852

http://www.gunsinternational.com/Holland-&-Holland-8--BORE--Double-Rifle.cfm?gun_id=100060388