Franchi, according to the Blue Book, they do knock something off for a BL-6 skeet, but not a lot. And I'm not sure whether the skeet guns were heavier or just choked differently. I do know that BL's in 28ga are pretty rare, in any grade. If I recall correctly, Thad Scott had a BL-3 28ga a few months back, price about the same as the asking on your BL-6--and Thad's prices tend to be on the reasonable side.
A 28 choked skeet/skeet probably wouldn't be a great dove gun, but I sure wouldn't reject one for grouse and woodcock, or quail. If you have a bore and choke gauge, it'd also be interesting to see just what the constrictions are.
