Tub Overflow leaks to downstairs

40 year old home with leaking overflow on upstairs tub in home I just purchased. Other than obvious dryrot issues I may find what might I find to fix leak. Tub is mid 1965 American Standard and hardware is Moen.

You should read the thread w/ the same question here from yesterday.
The question is why is water going through the overflow?
Do you fill the tub up to the limit every bath?
Where is the water coming from and where is it going?
Some pictures help here.

tub overflow fitting

Water is not leaking out of front of overflow fitting in tub like other post, water goes into overflow fitting and leakes out the back (hidden in back of wall) running down into the ceiling below.

Sounds like you are going to have to tear part of the wall out and take a look, unless the tub has a removable skirt. You might be able to remove the front trim of the overflow and take a look in there with a flashlight and maybe a small inspection mirror - you might find that it has cancer or if plastic, cracked. If you are really lucky, you might just need to tighten something up, but I doubt you'd be able to get to it without tearing out a protion of the wall. Maybe someone else will have some otherideas.

How old is this, and did it ever work right?