Combine almonds and sugar in a small skillet over medium-high heat; cook and stir until sugar is melted over almonds, about 3 minutes. Spread almonds in a single layer on waxed paper to cool.
To make the salad dressing, whisk together the vinegar, salad oil, sugar, mustard, poppy seeds, and salt in a bowl; set aside.
Toss together the romaine lettuce, spinach, mushrooms, Swiss cheese, onion, and oranges in a large bowl. Sprinkle almonds and drizzle dressing over top of salad just before serving.
