We’ve had this/these Leitz Trinovid 8×20 binocular(s) approximately forever:
The logo indicates we bought them before Leitz became Leica in 1986…
Recently, the eye cups became difficult to pull out. The problem seemed to lie in the seal around the exterior of each tube, rather than with the internal mechanism, so I eased the tiniest possible drop of clock oil into each gap, spun the tubes, cycled them in-and-out, and wiped off essentially all of the oil as it spread over the exterior of the tubes.
The eye cups work fine again!
Frankly, I felt a like a Visigoth upgrading the Large Hadron Collider, but I trusted those old-school Leitz engineers would protect their optics from everything happening outside the sealed tubes.
The new Leica Trinovids carry 8×42 optics, with 8×20 glass in the Ultravid Compact Field Optics line. They’re definitely spendy, but probably less in constant dollars than the ones we have; in any event, they’re definitely a a buy-and-hold investment.