Here is part of a collection I picked up last weekend. I can't say I have ever come across a collection of just blue mud before. Apparently the seller found them buried in the dirt under a shed. Penelec used blue insulators extensively on their old 4.16kv system, which is where I believe these came from. There are a lot of Lapp and Westinghouse pieces in the collection, but there are some some Hartford Fiance A107s and Pittsburgh U-600As there too.