Below is the info from George back when it was at Champlin. When I talked to George about it (years after he had it) he said in his opinion, the Dumoulin Imperial magnum and the New Mauser magnum action are the best, most solid actions for big DG chamberings and that if he hunted buffalo for a living, that's all he'd use given the option. He added that he especially liked that it was Dumoulin built, not just a Dumoulin action. So for whatever that is worth to someone, it was worth quite a bit to me considering where it came from.
"Henri Dumoulin & Fils - Belgium: A 416 Rigby Model Imperial Magnum, Built 1987 by Dumoulin on their true Magnum Double Square Bridge action, These Imperial actions are a full 1/4" longer than a Commercial Mauser Magnum action for proper function and feeding, 24" barrel with a 1/4 rib with 1 standing & 2 folding rear sights, Barrel band sling eye, Barrel band front ramp with a lock-on sight protector, Professionally installed claw mounts in our shop by Mr. J.J. Perodeau, Mounted with a Swarovski Z6i 1-6 x 24 scope with their illuminated reticle, Hinged floorplate with a frontal bow release, Belly magazine that will hold 4 down, 3 position Model 70 type wing safety on the bolt shroud, Double steel crossbolts, Classic style stock with point pattern checkering, Shadowline cheekpiece, Trapdoor steel grip cap, Ebony forend tip, 14 1/4" LOP over a 1" pad, 10 lbs. 2 oz. without the Swarovski and 11 Lbs. 6 oz. with it mounted, Original factory satin blue on the action and barrel remains at 99%, Original factory stock finish and it remains at 99%, The checkering is at 100%, The bore is excellent plus. This is a well-built tough rifle with a true full-length magnum action that will handle any length 416 Rigby cartridge which could be ideal for the handloader. Excellent action, excellent inletting inside & out, proper weight, excellent claw mounts, belly magazine and built tough to go the distance for serious big game hunting."