Always check drained oil from your transmission!

Roger that!! Even after 45 years of warnings, an occasional owner will still drain the diff lube and find an unsafety-wired ring gear bolt head... or three. Loose metal chunks can cause the aluminum ZF cases to crack open like a walnut if your luck runs out. Sure, its fixable but never cheap nor much fun on either end.

 While little pieces of metal are obviously not something you want to find inside any mechanical device, one could assume the snap ring itself is still in place and in no danger of coming off. 

 Unless you know the full history of your car that could even be a piece of a clip that was found broken and replaced during a rebuild. But the little broken off portion was somehow overlooked. 

 Unless your ZF is making funny noises or is somehow mis-behaving I don’t really think there is anything you need to do at this point; other than having the entire thing disassembled for a full inspection and that seems totally unnecessary. 

🤞🤞🤞

Larry 

 Is it a broken end of this circclip that holds the roller bearing in side covers? 

There is plenty of room for it to drop in the pan to the magnetic drain plug directly below it. . If just the end of the clip stressed from past squeazing you are fortunate to get it out .  Hopefully it didn't bounce around too long in the  bearing area and made a quick exit. 

Broken snap ring identified... ;-) 

I've seen small bits of metal like that snap-ring end get tangled up in one of the  synchronizer assemblies and lock up the shifting. That's if it avoids getting caught in the ring gear mesh and cracks the case. Pull the trans, take the bottom off and inspect it- or find someone who can. Crossing your fingers and hoping may not save your ZF. And they're not making any more.....

Where is the other 1/2? Can you pull back with this picture? Type 1, right?  Are we looking at 5th on the input shaft? I would be more concerned on why it failed at that location. Is there a locking pin on the shaft to keep the retaining washer from spinning?  I have only done 1 type one and that was many years ago.