I was looking through some recipes from one of my Grandmother Snarr's vintage church cookbooks. Check out this one for green tomato pickles.
Take firm, smooth green tomatoes. Slice and sprinkle with salt overnight. In the morning, pour clear water over and drain at once. Be very sure to get all water out so as not to weaken vinegar. Then pack in layers with white mustard seed, plenty of horseradish, cut up fine or ground, and small bits of green pepper, allowing about six to 1 peck of tomatoes. Cover with cold vinegar. Tie cloth over jar.
Will keep without sealing.
I remember Mrs. Jackson. She lived to be very, very old, so evidentally the pickles didn't do her any harm.