In a large pot boil the potatoes whole until they give when poked with a fork. About 45 minutes. You want them to have some give, but not to be mushy, you want them to hold their shape when cut up. When the water starts to boil I gently place the eggs on top of the potatoes for 10 minutes until they are hard boiled and then remove them with a slotted spoon. This way you don't dirty up 2 pans. When the potatoes are cooked remove from the heat, drain and set aside to cool. When the potatoes are cool enough to handle gently peel them and cut into cubes and place in a large bowl. Melt the butter and pour over the potatoes and gently stir to coat. Now chop up your eggs, onion and pickles and add to the potatoes. Add the mustard, mayonnaise, celery seed and about 1 tablespoon of pickle juice and stir to incorporate. Salt and pepper to taste. I used about 1 Tablespoon of salt, I know that sounds like a lot but there are a lot of potatoes here and you want it to be flavorful. Refrigerate couple of hours before serving.