Washer inside coolant expansion tank

I am replacing hoses and I had my coolant expansion tank out.
Gave it a nice cleanup and was drying it off and I heard a rattle inside it.
I found there is a brass washer inside the tank about the same size as the throat of the expansion tank brass fitting
that the pressure cap screws onto.
My concern is that washer was suppose to be swaged onto the inside of the pressure cap inlet and it has come free.
...
Should I get a new expansion tank (before the throat pops out from pressure)?

TIA as always - Al

take a pic..... the best way to tell if its time to replace the tank is the color.... if its yellow-ish then its time. and if things are poping off then it past the due date

Thanks Shawn - The fittings were yellow - tank seems clean - Don't want to miss out on driving once it's ready.
Ordered a new tank today.

Al