For the field, this is a file for the japanese PSX version only, it adds text characters. In the PC version, the file sysfnt.tdw in main.fs is used to know the width of each character, the texture part is not used (you can find the used texture in sysfnt.tex in menu.fs).
|0||4 bytes||Offset to widths (always 8)|
|4||4 bytes||Offset to data|
|offsetWidths||offsetData - offsetWidths||Character widths|
Each width is 4 bits (two widths per byte).
Texture is a TIM file with 8 colors: dark grey, grey, yellow, red, green, blue, purple and white.
TODO: Explain the palette mechanism in japanese version (16 pal instead of 8).