This was a most unusual early radio design. Rather than change channels using a variable capacitor, they used variable inductors. Quite unique.
On thing about those old radios, they always had HUGE coils. Even those that tuned using a capacitor. Apparently they would all coils by hand back then, and could not wind small ones like they used in later model radios. Not to mention they did not use ferrite cores like later radios.
When I was a kid, I had some of those old HUGE coils that someone gave me, along with other very old electronic parts. I wish I still had them....