I had broken my wrist in late April, and just yesterday was finally able to hit the gnarly "gravel" (extremely coarse "gravel") trails alongside a local railroad route using 7sp GRIPSHIFTERS (model 300) from 1992, with plastic indexing springs still in the game (since I replaced them 6 years ago).
With my still-lingering wrist injury, I could only do one shift at a time, but the weak-ish indexing got the job done and I only got bogged down a couple of times.
These shifters have a LOT of use on them over 20 year's time, and only the plastic indexing springs ever wore out. They're so old that the cables exit straight down, and they came on this ProFlex model 253 (rear-only suspension) hybrid that I remember buying on close-out for $299.

I should mention these shifters are very light. Even the left/front shifter on these is indexed for triple, and the longer-barelled grips are a soft solid rubber, sans any sort of tread. An even longer-barrelled version appeared later, in the early 9-speed era, but by then they used the 1:1 actuation ratio and of course had steel springs for race-quality index detenting.

One thing about the Shimano-compatible (and earlier models) of Gripshift is that they need a special "jonnisnot" grease to work properly, elsewise the "sliding ramp" innards don't slide any too easily. Ordinary greases, even "Teflon" greases, won't work, but certain modern suspension-specific greases may work well enough.

Ahhhh, the memories!

Yep, I love my Grip Shifters on my MTB they've been on my Giant since 97 and I have done zero maintenance on them. Still have the original cables and they still work without any issues.

I have a French "EGS 3X7 Synchro Shift" grip shifter that is supposed to shift both the front and rear derailers simultaneously. I've never tried to make it work or even taken it out of the original packaging.

Huret Allvit.

Seriously.

People compare these to 1985 Dura Ace rear derailleurs and find them lacking. Duh. Compare it instead to its actual time period and price point contemporaries, like the Campagnolo Valentino, a plastic Simplex, any pull chain rear derailleur, the Shimano Archery or the SunTour Skittern.

"Brilliantly engineered." Frank Berto

"I found that the Huret Allvit shifts very well. It was used on such diverse bikes as the most expensive René Herse randonneurs and relatively inexpensive Schwinn Varsity." Jan Heine

The unique Allvit is really a cool rear derailer. It features:
1. A parallelogram action that moves down as it moves in. This allows the guide pulley to maintain an equal distance from all the freewheel cogs for accurate shifting - well, on 14-28T, 5-speed freewheels, anyway.
2. A guide pulley that is mounted co-axially with the cage pivot. The guide pulley doesn't change its positions relative to the freewheel cogs when the front derailleur is shifted. This allows consistent rear shifting even with large size differences in the front chainwheels - a basic good geometry in contrast to most other contemporary derailleurs.
3. A derailer body that forms a protective cover over the working parts.
4. A well thought out, highly produceable design for manufacture - there is really only one part, the main control arm, that can't be stamped from sheet metal or turned on an automatic lathe.