If you compare the H&H with your gun you will see it has a totally different shape to the action. The H&H has the bottom corners of the action rounded All the way back to the wood, this gun does not. There is no sculpting at the front of the bar on the H&H, it has essentially the same shape for the entire length of the action body. The H&H has a back action lock so the mainsprings do not lie in the frame bar. This Dumoulin from the pics appears to be a bar action. It would be I believe rather difficult to make a round action using a Bar action sidelock. Most round actions are either a trigger plate action or back action sidelock.
Understand I am not knocking your gun because it is not a round action, I have never owned a Round Action Double. I have several with a similar shaped action to this one though not of the same high quality. I just do not see it as being classified a Round Action.
