Here is the 28ga version of the gun you are considering, this one is from the late 1940's.
The only change is the addition of side-clips. This one retains much of it's case coloring.



Henri Pieper held many patents in Belgium, Germany, England and here. One of them was for his method of joining barrels.
This is his earliest demiblock or chopper lump, this is a 10ga. He was so proud of it that the rib bears the patent date, April 23, 1881.
Notice that the demiblock is fluid steel, the tubes are damascus and the muzzle is fluid steel.



He later modified and improved this method to look like this, in 1892.


For general gun related definitions:
http://www.hallowellco.com/abbrevia.htm

Here are some close ups with explanation and diagrams:
Monoblock
http://www.hallowellco.com/monoblock_barrels.htm

Chopper block
http://www.hallowellco.com/lumps.htm

For some reason, people generally refer the demiblock (aka Chopper Lump) as being of Italian origins, which is not the case.
Though Beretta and others Italian makers later adopted this method.

Peter