EPOC Application Information File (AIF, or Symbian AIF) is a format used on EPOC/Symbian operating systems to store an application's icon and caption. Apparently, it is sometimes used as just an icon format, without an associated application.
The images use the same internal data structure (sometimes called "Paint Data Section") as EPOC MBM and EPOC Sketch, but other parts of the format are different. Each icon is composed of two images: a foreground image, and a transparency mask.
Some AIF files begin with bytes
37 00 00 10 6a 00 00 10.
Others apparently begin with
37 00 00 10 38 3a 00 10.