Mix gelatin, 1/4 cup of the sugar and salt thoroughly in the top of double boiler. Beat egg yolks and milk together. Add to gelatin mixture in top of double boiler and cook over boiling water, stirring constantly until gelatin is dissolved, about 5 minutes. Remove from heat and stir in vanilla. Chill, stirring occasionally until mixture mounds slightly when dropped from a spoon. Stir in coconut. Beat egg whites until stiff. Beat in remaining 1/4 cup sugar. Fold in gelatin mixture. Turn into baked pie shell and chill until firm. Garnish with whipped cream if desired. To quick chill gelatin mixture, if you are in a hurry, set container with gelatin mixture in a bowl of ice and water and stir until it thickens or place container in freezer for 5 to 10 minutes. Be sure and fold gelatin mixture into egg whites so mixture will stand up and be more fluffy.