What is the longest piece you've seen?
I just finished looking at an early 18th century Dutch gun with a 111 inch long barrel, a 78 caliber smooth bore, 126 inch overall length, and slightly ornate furniture without engraving. At first glance I assumed it was going to be a wall gun; however; it's bore is fairly small for that purpose, and it has no evidence of a hook or swivel for firing from a wall. The other wall guns I've seen have also had plain military style side plates. Obviously this beast couldn't have been fired off-hand. I can't get pictures of it, but the lock is signed by Filippe de Selier of Liege (active around the 1690s-1720).