The first Republic stamps were issued on what was orginally referred to as Independence Day celebrating the Treaty of Manila which granted Philippine Independence for the United States on 4 July 1946, this was later referred to as Republic Day and subsequently Philippine-American Friendship Day.
The stamps issued in 1946 marked the beignning of a new era of collecting referred to as the "Republic of the Philippines" (technically it was the start of the 3rd Republic with the present day in the 5th Republic) and the issuing of stamps no longer under foreign juristiction.
This first set of stamps possibly violated the UPU rule of identifying the issuing country. The stamps stated “Independence of the Philippines” instead of just the country designation “Philippines” or “Republic of the Philippines”. The three values of 2c, 6c and 12c, depicted a Filipina with the Philippine flag, and behind her, flags of different nations.
The 70th Anniversary was celebrated by the Post Office during the National Stamp Collecting Month (November) with an issue featuring images of the original 1946 stamps.
National Stamp Collecting Month 2016: 70th Anniversary of the First Stamps of the Republic of the Philippines #3688 and 3689, 21 Oct 2016