PI3AA 1926 Philippines
The operator Fred Johnson Elser (1906 - 1988) held several callsigns through the years. In the Philippine Islands 1ZA, PI-3AA, K3AA; in Japan after WW2, KA2DX and later Stateside, W6FB, W7OX and KH6CZ.
There is also an article about him called Elser-Mathes Cup awaits on the ARRL website.
Courtesy of KB4SAD