GC3 file extension is for Golden Common Lisp 3.1 Lisp language source code file
Similar to GC3
#ST - LocoScript Standard mode printer definition file
$$P - OS/2 Notes file
$$S - OS/2 Spreadsheet
$00 - DOS Pipe file
$1 - ZX Spectrum file in HOBETA format
$D$ - Data
OS/2 Planner
$DB - Temporary file
dBASE IV
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