Actually a good question Ed and the answer, I think, is "because it's big."

I have two 2 frame Parker 10 gauges and enjoy them.

i have taken some clays with Craig's gun- once you get it moving (which is not difficult) on a long target - you won't stop your swing

i expect the weight was to soften high volume shooting of heavy loads

I have asked myself that question many times and wish I could ask the original owner. Both my 6 frame guns have were used extensively. Untold numbers of waterfowl have fallen to these two guns. The other oddity is a market hunter wouldn't have the resources to buy a D. I have shot ducks with both and they are quite easy to handle in the blind. I see no real advantage to their size except the original owner wanted a heavy duck gun that may have been similar to a 8 gauge. For me they are a extremely interesting part of the golden age of duck hunting.

One of my #6 frame guns is factory bored for 3 1/2" ten gauge shells. It is an early gun, I think before the introduction of 3 1/2" factory magnum shells. Apparently the buyer was reloading some big stuff.