Early 1960’s, USA. Trusonic (or Tru-Sonic) bells were made by Benard Mason, an ordained Baptist minister and music evangelist of Glendale, CA.  The castings look like modern bells.  Handles and handguards may be black leather or white plastic with gold pitch designation letters.  As you can see by the picture, the clapper mechanism almost looks like a hybrid between Schulmerich and British clappers.  The springs are similar to Whitechapel, but the striker is a round, leather covered disk, fastened to the rectangular clapper shaft with a washer and screw.  A440

Below also is a one octave diatonic set (C5-C6) of Trusonic 4-in-Hand bells.  The photos for these bells are courtesy of Mark H. Shour.