Reference collection
A reference collection is a collection of objects maintained for the purpose of study and authentication. Reference collections are generally large undertakings maintained by institutions; instead of having a single representative of each object, they will typically have multiples, so as to illustrate variations and, sometimes, provide samples for comparisons. For human-created objects such as postage stamps or coins, a good reference collection will also include an assortment of (carefully labelled) fakes and forgeries.