Spinach and Bacon Salad with Sweet-and-Sour dressing

This is my favorite salad and salad dressing -- my mom has made it for years, and it really goes well with a wide variety of foods.

SPINACH SALAD WITH SWEET-SOUR DRESSING

fresh spinach
crumbled bacon (amount to taste)
croutons
3 or 4 hard cooked eggs, chopped

DRESSING

1 Teaspoon salt
1 teaspoon pepper
1 medium onion, chopped (can use ~2-3 Tbsp dried minced onions)
1/2 teaspoon celery seed (celery salt can work in a pinch)
1/3 cup cider vinegar
1/3 cup oil
1 & 1/2 teaspoon prepared mustard
1/2 - 2/3 cup sugar

Mix torn spinach leaves, bacon, croutons, eggs in bowl (croutons get soggy if not being used right away).
In blender or a shaker, mix together dressing ingredients. Pour over salad. Serves 6-8 persons or more.
NOTES:
Dressing keeps well in refrigerator for several weeks.
Can make lots of good variations:
Can omit eggs and/or add sliced mushrooms, tomatoes, pecans, dried cranberries, dried cherries, onions, chicken, etc, etc!