It's probably common knowledge to everyone except me. Searching didn't produce anything.

So, what's the purpose? To tell the driver they can shift from 1st to 3rd?

Spring loaded stop at that location.

Makes sense.

The funny thing is there's no way I would have figured that out with the condition of my shifting. The spring loaded plate doesn't engage till half-way to 4th/5th. I found out why (no the car hasn't been driven in 8 years... yet)

is that the shifter console or at the back of the trans? If thats in the shifter console That peice should not be there

It's the ball cup bushing that the shifter sits in (tail shifter). It's just unrecognizably trashed.

replaced that bushing last night, hope to have 1st and reverse now.

AKA "Reverse Lock" - but in this case it also "locks out" 1st. Put in there to guard against accidental downshifts into 1st or R, esp. when racing - form which this 901 shift pattern was derived (from Porsche race cars' transaxles). It means you have to push a bit harder to get into that gate..

Tailshift has a cup up front too; sideshifter does not.

Ohh I was wondering, that makes sense since mine doesn't have that cup up front.