Here's the full list from object/GSgopherobj.h:
#define A_FILE '0' /* Types of objects */
#define A_DIRECTORY '1'
#define A_CSO '2'
#define A_ERROR '3'
#define A_MACHEX '4'
#define A_PCBIN '5'
#define A_INDEX '7'
#define A_TELNET '8'
#define A_UNIXBIN '9'
#define A_SOUND 's'
#define A_EVENT 'e'
#define A_CALENDAR 'c'
#define A_GIF 'g'
#define A_HTML 'h'
#define A_TN3270 'T'
#define A_MIME 'M'
#define A_IMAGE 'I'
#define A_INFO 'i'
#define A_MOVIE ';'
#define A_PDF 'P'
#define A_WORLD 'v'
#define A_APP '!'
#define A_EOI '.'
.