What mint has no mint mark for 1927 double eagle?

Your 1927 Double Eagle was minted in Philadelphia. The Philadelphia mint used no mint mark prior to 1942. In 1942 the letter "P" appeared on the reverse [tails] side the Jefferson Nickel. It was used during the war years of late 1942 through 1945 when nickels contained 35% silver and no actual nickel. After 1945 the Philadelphia mint again used no mint mark for the coins produced there until 1979. Again, the letter "P" appeared but this time it was on the new Susan B. Anthony Dollar. In 1980 it was decided the letter "P" should appear on all coins minted at Philadelphia except for the Lincoln Cent.