I recently acquired a couple of Peltor 8003 headsets secondhand. They
have two stereo jacks. These are molded on so I cannot open them up to
see what happens inside.

I took the quarter-inch to be stereo, but no: I measured some 290 ohms
from tip to ground, and nothing between ring and ground. And indeed a
signal on the tip will be heard on both sides. Is anything wired to the
ring? If not, why did they bother to use a stereo jack?

I'm still more baffled by the microphone jack: perhaps the ring is a
provision for a PTT-switch?

Thanks in advance for any enlightenment,