What are these?

[Les]

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I took one apart and there are copper plates, springs, insulation plates (bakelite), etc. the box is a standard cigar box for scale.

[Marc]

My guess is that they're crystals. Each vibrates at the specific frequency that's marked on it. Frequency generators that are used to power transmitters (ham, public radio/tv, police, etc) normally drift around a little. The crystals hold them on target.

Transmitters need to transmit at specific frequencies within extremely tight tolerances, otherwise receivers might miss it, neighboring spectrums become polluted with your trash and if the FCC catches it, they triangulates your location and come knocking on your door.

Apparently, the guy who owned that box of tubes, etc worked on transmitters.

Marc

[Nolan Kienitz]

Crystals for the frequency noted on the case. They were cut to oscillate/operate only at the specific frequency.

Tunable VFOs were not available back in the day.

There are some ham radio operators who build QRP (low power) rigs that are crystal based and when they post for a QSO (conversation) they say they are "rock bound" ... as they are using a crystal.