Producers of new things have always required a method of documenting the progress in their development One of those methods involves assigning development shop numbers at key points in progress. Here are examples of shop numbering from the Sheaffer's factory in Fort Madison, Iowa. All are mechanical pencils. Circa 1920's-1930's. Showing top to bottom is a Sheaffer's sub-brand Univer, followed by a Sheaffer's and lastly two Sheaffer's Wasp sub-brand pencils. Disclaimer: There are no bends in the pieces, just disappointing optics.