Oldest gear still for sale is . . .

You are correct yogiboy, I got "still for sale" mixed up with "production."
Kenny

That’s right gentlemen. We’re not talking T-Rex or Sabre Tooth Tiger here. They stopped making those models a long time ago. What we’re looking for is a Crocodile - was here, way back when they were making the T-Rex, and still in production today.
Racking my brain to come up with the oldest, yet current, audiophile component I’ll throw out the SME, S shaped, tonearm. (I consider it to be a component, rather than just a part).
I know when I put together my turntable-base-tonearm-cartridge system in 1980, the SME had been around for a few years already - a little longer than the Shure V cartridge, if my memory serves me well.  The tonearm has seen a little improving over the years but no radical change from the early 1970s.
I’ll say that’s my Crocodile.

I wish we could say the Shure V series. They should never have stopped making it, even if they had to change the cantilever. 

Does anyone know when Jelco started selling the SA-250ST? It had to be in the 1980's, right?

I personally am using a Stax SR5-SDR6 electrostatic headphone system, McIntosh MR74 tuner, and a Yamaha CA800 integrated amplifier on a third, small adio system.  What all there of these have in common, besides all of them at least 35-40 years old is that they are still incredible.  Trully, totally.  So much of this "old" stuff is still in excellent condition.  Used with todays latest power cords, power conditioners, interconnects, speaker wires, etc., some of these "ancient" audio products are definitly not out of place today.  I can still remember 40 years ago the Yamaha CA1000 integrated amplifier was being praised for it's preamplifier and matching phono preamplifier attributes.  And, in fact, my present Yamaha CA800 integrated would be hard pressed to be equalled today for less than say $2-$3000.  My Stax headphone system, for which I paid $100, sounded very like a $2000 Audieze pair of headphones I once heard.  And my MacIntosh MR74 tuner-well I recently sold my Day/Sequerra as it was nowere being it's equal.  No, for the money, carefully selected "old" stuff can be hard tobeat.  And lots of this can be found in basicsally mint condition.  And, of course, old timers such as myself are dying right and left  all over the place.  So the current situation should continue for some time.  And their prices are sure to be going up as more of us realize what treasures are outtheir for the picking.

Not many components can say they have been in commerce for a long time, but haven't become dated and superseded by more current gear,

The SME V arm came out in 1985, was considered one of the handful of top tonearms available, and continues now, 32 years later in the same company.  Hard to think of any other component that has not only continued in production but has also held its place vis a vis newer gear.