Quality standards in our hobby have remained static for so long that there are few collectors active today who are aware that the standards that seem so normal today have really evolved over the last century of collecting. The earliest collectors had no quality standards to speak of. Any copy of a stamp, no matter how poor, was deemed collectible. Stamps were often peeled off of envelopes, leaving many collections of the period showing examples of stamps that were mere pieces. The earliest collectors didn’t use hinges or mounts either. They gummed their stamps directly into their stamp albums making for many damaged stamps when they were removed.
The first revolution in quality began about 1890. It was concentrated around the idea that collectors should try to preserve their stamps in a quality as close to the quality that they were issued in as possible. Stamp hinges began to be used to allow collectors to sell and trade their collectible stamps without damage. In stamp price lists of the 1890s, we see for the first time stamp faults being listed, resulting in the price of the item being discounted from perfect. By 1920, there was a clear delineation between the price of first quality stamps and the value of similar stamps with faults.
The second great revolution began about 1920 and related to centering. Stamp collectors had previously simply wanted a copy of each stamp. Beginning about 1920, collectors began to esteem centering; the more perfectly centered the stamp, the more demand for it and consequently the higher the price.
The last great quality revolution began about 1960 and was fully consolidated by about 1975. It related to the gum collecting phenomenon that Americans call “never hinged.” Before 1960, it was universally accepted that collectors had to mount their stamps somehow, and the accepted method of mounting was hinging. By 1975, collectors of the highest quality were demanding never hinged stamps, and collectors began using stamp mounts to protect the precious gum of their stamps. This has meant that many of the rarest stamps from the pre-1960 period which were put into collections when hinging was common are rarely found in never hinged quality. They only exist from the odd stamps that were stored in stock books or from blocks that have been broken to obtain the never hinged stamps.
The effect of the increasing quality emphasis of the last hundred years has been the narrowing of the supply of stamps that are of the highest quality. Out of each hundred of the scarcer stamps that were issued in, say, 1900, less than 10% have what we would call today Very Fine centering and no faults. Of those ten, maybe one was never mounted in a collection before the never hinged phenomenon took over collecting. So perhaps one out of hundred issued stamps of 1900 could be deemed perfect today. And some experts would consider my estimate to overestimate greatly the number of VF, NH stamps from before 1900.