It's probably a 75. Other tubes that look similar are 2A6, 55 and 85 but there are differences. The first two have 2.5 volt filaments. The 85 has lower gain but much higher emission.
Norm
:Hello, still working on the unknown radio. Is it possible to test this tube as a 75 and have it test good when it is not a 75. It is a philco tube, but the only indentifying marks on it is the penciled"75"on its base