or just label with the inductance and put 'em in the parts pile.
That's what I do. Especially if they have been removed from equipment, because a lot of
such coils are
custom-wound for a specific product, and are marked with the
manufacturer's house number.
I use an FET Colpitts oscillator designed for about 100pf effective across the inductor,
measure the resonant frequency range as the core is adjusted, calculate the inductance
from that, and mark it on the side of the can with a felt tip marker. This has an advantage
over some inductance meters that operate at low frequency, as the core performance
can vary with frequency.
There are three common construction methods for canned coils such as these: the "cup"
core (the top of the core takes up most of the top of the can), the standard core (a smaller
core down the middle of a coil on a small former), and a VHF style where the turns are easy
to count if you remove the can, the core is often aluminum (or missing), and the color of
the insulating plastic former may be used to identify values in different coil families.
The "cup" cores often have inductances around 700uH for 455kHz IF transformers with
secondary windings and an internal capacitor. Red cores may have lower inductance
and no secondary winding and no capacitor - these are for the local oscillator. Interstage
transformers are often color coded by application, but the color codes aren't universal
(especially for custom products.) It is worth checking, however.
The small standard cores are often 10.7 MHz IF transformers, typically with a powdered
iron core rather than ferrite, and are more suitable for HF work.
VHF coils rarely have secondary windings, and usually have just two pins on opposite corners.
Here is a link that shows some coil types and rewinding recommendations:http://www.intio.or.jp/jf10zl/ozlcoil.htm
I would say that his type A coil is typical of a 455 kHz IF transformer, and his type B coil
is a 10.7 MHz IF transformer.
The 10.7 MHz transformers and coils can be used on 40m and 80m simply by adding some
capacitance across the coil. I've also rewound the 455kHz coils for 80m (it only takes 20
turns or less on the ferrite) but find that they aren't as stable for VFOs. In some cases
there is enough frequency shift due to the effect of the Earth's magnetic field that one
can hear the pitch of a CW signal change as the antenna is rotated.