Vintage shell necklace hangs 13" slips on

This is a vintage hand made shell necklace . Native with bead in front. Slips on no clasp . Hangs 13" . Chunky shell . This was my grandpa's . See listing will bundle all native items from his vintage collection . Not exactly sure of the date but at least from 70's-80's possible a lot earlier . Either NW native or Alaskan .