2 pounds medium shrimp (about 64) shelled, and, if desired, deveined
1 lemon, sliced thin
1 onion, sliced thin
a 3-ounce can pitted black olives, drained and sliced
a 2-ounce jar pimientos, drained and chopped fine
1 cup fresh lemon juice
2 tablespoons white-wine vinegar
1/2 cup vegetable oil
1 teaspoon salt
1 teaspoon freshly ground black pepper
1/4 teaspoon cayenne
1/4 teaspoon dry mustard
1 bay leaf, halved
Into a large saucepan of boiling salted water plunge shrimp and simmer until just cooked through, 1 to 2 minutes. Drain shrimp in a colander and rinse under cold water. Pat shrimp dry and transfer to a large bowl. Add remaining ingredients and combine mixture well. Marinate shrimp mixture, covered and chilled, stirring occasionally, at least 1 day and up to 2 days.
Discard bay leaf and serve shrimp chilled.