.3S File Extension Information

What program uses .3S file extension?

Program : Advent 3B2 Paragraph Styles
Program Website: Advent 3B2 Paragraph Styles

Extensions starting with

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | #-0-9