Ok I found it, it needed a real good clean, which I've done.
Good news, it's intact, the alloy outer part usually breaks on the lip where the seal fits but this is intact.
The worm drive is also intact and the cable cinch is in great condition, they usually get clobbered by the drive chain and distorted, the cinch was siezed but it's lovely and free now.
The seal was still on the alloy part and is in remarkably good condition considering it's age, rubber is still soft.
The worm drive and outer housing work perfectly when moved by hand, goes in and out as it should.
Now the bad news,
The alloy has suffered due to poor storage, it was a little furry to say the least, however it's still ok, just a little pitted. The outer part you can see from the outside is perfect, it's the part hidden inside the casing which has suffered.
The metal worm drive arm was rusty and is a little pitted but still strong.
Now the really bad news,
The ball bearing which sits inside the worm drive is buggered I'm afraid, too rusty to save, I tried, even gave it CPR but it was pronounced dead on arrival. Sorry about that, good job I have some new ones.
I used to have a few of these NOS, must have sold them.
I did find another still in that casing BTW but I've left it there until it's needed.
I'll post a pic of the drive tomorrow. See if it's good enough for you.