I pulled out my Trans dip stick and noticed a small metal washer sliding freely on the dip stick followed by a rubber/plastic bushing that keeps the dip stick secured in the tube. Are there any metal parts in front of the small round washer that mite of ended up in my Trans?

Also can I mix synthetic ATF +4 with the factory fluid thats in my trans?

 

Nothing in front of washer on tube.
All atf+4 are mixable.