Pack the chilies in two 1-quart jars and cover them with water to come within ½ inch of the rim. Pour the water out into a measuring cup. Note the volume, pour off half the water, and replace it with sherry vinegar. Add 2 tablespoons sugar and 2 tablespoons salt for every 3 cups of liquid.
Pour the vinegar mixture into a nonreactive saucepan and add the bay leaves, coriander seeds, black peppercorns, cumin seeds, marjoram, and garlic. Bring to a boil over high heat, then reduce the heat and simmer for 10 minutes. Remove from the heat and let cool slightly. Pour the hot liquid into the jars to cover the peppers, and screw on the lids. Refrigerate for up to 1 month.