Mouat Water Seal System Booklet
Keep in mind when viewing this booklet, that the Mouat Company had more than one style of steam heating system and yours may not look exactly like the one described in this booklet.
This booklet is a sales booklet with a brief description for the original steam system that had graduated inlet valves for the steam, and water seal return ell's at the other end of the radiators. Water seal return ell's are NOT steam traps.