It pays to study your Scott US Specialized catalog. Have you noticed Scott #2400, the 25¢ Sled Riding stamp?

There is a cylinder flaw (i.e., plate variety) where the curlicue is missing. It only happens on two positions on the printing plate. Both are listed in the catalog for $15 and $10 mint. This is a common stamp and unless you’re paying attention to detail, this could be easily overlooked. At $10 and $15, it’s uncommon, but not rare. You won’t be a millionaire, but if you keep your eyes open, you could find a more valuable plate variety.