Please Identify this adjustable inductor (ferrite-core bobbin)
Per @TimWescott in the comments above, they are (or are similar to) these.
He also notes that &quot;Variable inductors just aren't current tech, and variable capacitors are getting few and far between -- technology is just marching away from that sort of circuit design.&quot;
Edit, Here they are:

At least for the moment, they are available here in packs of 20.  I'll post model numbers when the arrive if they are listed on the label so we can know what manufacturer actually provides them.
Plastic Inductor Bobbin
Ferrite Screw for the Bobbin
#2, #3 do not have shields, but #1 does.


Here are a few other resources,  in case someone finds them useful:

Material and Winding Reference
Another (but different) material and winding reference
&quot;Secrets of RF Circuit Design: Chapter 4: Winding your own coils&quot;  references the Amidon model number and gives the number of turns.