Picked from the LCS junk box last week. Knew right away it was going home with me 1966 Panama 1/4 Balboa https://en.numista.com/3034
Looks like the real deal. The reverse is good and when the obverse is missing the outer clad layer, the core is being struck and the details will appear mushy. Wow. Nice score. (And the correct weight.) There is a small fragment of the obverse cladding at 8 o'clock. It must have broken off before being struck? If it was "missing" there wouldn't be any.
I believe that it was once a Clamshell Lamination that went from one side to the other and attached like a hinge. Someone pried it and it snapped off. Hence the mushy details. A true missing clad layer would have a sharper strike. IMHO this is an intentional damaged mint error. Here is and example of a Clamshell Lamination on a quarter. The Panama coins were also minted in the United States.
I too believe this was a Clamshell Lam I added the picture that appears first after the original post just to show that leftover piece of clad
