And for posterity, the recipe

Pickled Pepper Rings

Prepare 5 pint jars and lids.

3 lbs. mixed sweet and hot peppers
5 c white vinegar
1 ¼ c water
5 t canning salt
5 T mustard seed

Wash and slice peppers in ¼ inch thick rings. (I deveined my peppers and removed most of the seeds).
In a large non-reactive pot, bring brine to a boil.
Place 1 T mustard seed in bottom of each jar. Pack pepper rings into jars.
Cover with hot brine, allowing ½ inch headspace.
Process for 10 minutes in boiling water bath.

Allow to age gracefully for 3 months.