I got some more info from the OP on the other forum. Apparently his Lanchester is modified to U.S. DEWAT standards, which I gather substantially reduces its value compared to UK/Canadian examples.
Some further information is needed. The U.S. DEWAT (DEactivated WAr Trophy) program was a thing back in the 1950's (in any case, prior to the Gun Control Act of 1968), which allowed certain machine guns to be "deactivated" and sold as non-guns. In some cases, the deactivation was as simple as filling the barrel with molten lead, and breaking off or welding the firing pin -- changes which could easily be reversed. The GCA '68 required DEWATS to be registered just like live machine guns, and, since that time, many registered ones have been reactivated. The ones that were not registered during the 1968 amnesty are now contraband.
Where is the gun located? If not in the U.S., the U.S. DEWAT standards never applied, and if in the U.S., the gun better be registered or someone's potentially in a lot of trouble. An unregistered DEWAT in the U.S. has no value (or rather, a negative value since possession of it could send you to prison).
I suppose the receiver could be torch-cut into three pieces and the "DEWAT" turned into a "demil." But this is not something you would want to advertise to the world. Before doing the torch-cutting, you would be in possession of something that could be defined as a crime.
I suspect you are talking about a "demil" rather than a DEWAT. In other words, a display or dummy gun built using parts of a cut-up receiver with the gaps filled cosmetically with resin or some other soft material. The British-style "deactivation" is quite a bit more sophisticated than that, but still results in a destroyed gun.