The Forum is always enthusiastic about Banker's Special revolvers. It's great to see your new acquisition. It does appear to be refinished but it is a good-looking revolver in the nice, detailed photos. The marking on the butt adds interest in my view.
The Banker's Special is chambered for the .38 Colt New Police and .38 S&W. Apparently the .38 Colt New Police is nothing more than the .38 S&W cartridge with some minor change to the bullet's shape. Someone will be along shortly to correct me if I'm wrong about that. It will also chamber and shoot .38 Short Colt with perfect satisfaction. I've shot several boxes of factory .38 Short Colt through my Banker's Special. I once put down a feral dog from fairly long yardage with a shot to the head using a factory .38 Short Colt in the Banker's Special. I was a bit surprised that it penetrated the skull. The load is puny. The .38 S&W is better. I think .38 S&W makes better sense than the .380 ACP. I like the heavier, soft lead bullet.
Here's some scanned snapshots of my Banker's Special. Hopefully all the Forum Banker's Specials will make an appearance, including the .22s.
I don't know the significance of the "DDG." The little revolver lettered to have shipped from Colt to the Tufts-Lyon company in Los Angeles on April 9,1932.