John;
You are really splitting hairs, the point I was trying to make was that the insides of any radio cabinet that I have owned was not raw nor untreated wood, shellac was only one of several coatings that may, or may not have been used on the inside, a dab of alcohol would quickly answer that question. There are also different grades of shellac, different cuts (ratio between pounds of shellac used per gallon of alcohol) and different colours, all with different characteristics. Like for instance, 78 rpm records were often mounded from shellac, they do not often warp, nor do they break down easily, even in humid environments, so clearly the mixture used is a lot more durable then white shellac.
In Zenith cabinets they used a dark blue paint, in RCA sets it was often silver paint, sometimes a dark brown, what the chemical nature was of these is unknown. Hide glue seems a likely candidate for a sealer, it was cheap and readily available in any cabinet shop. Casein was another popular substance used back in those days, along with some early man made substances. Again, the point being is that the insides of the majority of these cabinets was sealed with something, and it does not simply disappear, which means that odors would not necessarily penetrate the wood and could largely be removed by cleaning.
Regards
Arran

The issue is not whether or not the interior of a cabinet was finished when it was new. All finishes are fragile and, unless taken care of, deteriorate. No one takes care of the inside of the cabinet. There was no reason to take the same amount of care of the inside of the cabinet as the outside, so whatever was done was at most second-rate. Humidity and temperature changes alone will damage a finish after decades, even inside a home. Many old radios spent decades in garages, sheds, barns, and damp basements exposed to a wide range of temperature and humidity.

I mentioned before, I deal with wood that was first finished as early as the renaissance. 80 year old radios are new by comparison. I also worked with an R&D lab for 15 years studying material properties. For the last 15 years most of my work has been on computer models of the deterioration of materials for the DoD and a private international company. In both cases, billions of dollars are at issue. There is an inescapable law of thermodynamics that things, left to themselves, fall apart. The only issue is how long it takes in the environment in which it exists.

Lacquer, shellac, hide glue, and casein on wood all deteriorate in a time span of a decade or two. Lacquer yellows first, then crazes and cracks. Shellac does the same, only more quickly. Hide glue was useful with wood because it dissolves in water, making repairs easy. Casein is the most unreliable of the group because of its chemical properties. It is inherently acidic so it its mixed with lime to attempt to make it neutral. its behavior is affected by salts. I had a set of late 19th century French chairs that had spent years near the French coast and had been in storage. They were made using casein glue. While in storage the moisture softened the casein, which was acidic and ate away at the wood. Every joint was rotted from the inside even though externally the chairs looked fine. If you read about casein, you would discover itis hydrophobic. It has an isoelectric point of 4.6, which is the pH at which it has no free electrons, making it chemically neutral at that pH. This is fairly compatible with the acidity of wood which has a pH range of 4 to 5. Unfortunately hydrophobia disappears in the presence of salt, something that is in the air near the French coast. If the pH of the wood is different than the casein, things fall apart.

Since I don't know what kind of paint was used for the inside of cabinets, I can't say much about their deterioration, but you can read about the issues at this conservation site:

http://wccfa.com/glossary.html

What I can say for sure is that it is unlikely any finish used on the inside of a radio cabinet retains its integrity more than a couple of decades. It may still look OK, but at a microscopic level, it is porous.

John