In the September 2013 Precancel Stamp Society journal The Forum, I wrote a column about the Jekyll and Hyde that is
ebay. I showed pictures that exemplified the two extremes - these were Jekyll's. The parcel post was known to exist from early records but missing from all collections for 80 years. The 5cent is virtually unknown on attached pairs and a block is a spectacular rarity.

Finding them in one month on
ebay shows its amazing power to unearth weird and wonderful stuff. Uninformed sellers can get fair prices too, because the pictures tell the [nearly] complete story of what is offered.