Are you sure about what you have? The Philippines didn't issue a 50 Centavos in 1966.
The Philippines Republic decimal coinage started in '58. A 50 Centavo was minted in '58 and '64. A commemorative ½ Peso was minted in '61. That coin was Ag, the same specs as a U.S. half.
Their reform coinage started in '67. A 50 Sentimos was minted on and off from '67 thru '94. It was CuNi.
If I have the gift of prophesy, and know all mysteries and all knowledge, and if I have all faith, so as to move mountains but do not have love I am nothing. And if I give all my possessions to feed the poor, and if I surrender my body to be burned but do not have love it profits me nothing.
I left that one in my work locker.....but now I am looking at a 1971 version....and again...it has that "ring" of silver sound to it.....and it has that silver "toned" look to it.