Bed warmers were used to warm beds in the olden days, before the days of furances and central heating. Most households, if lucky, had a fireplace to warm a home, though the fire warmed only one room. Bed warmers were a necessity in cold climates like England, where it rains a lot. It is generally pretty easy to tell if a bed warmer is an antique or a reproduction, if you know what to look for. The main characteristic of a reproduction is an electric cord. Almost all modern bed warmers are electric, and from the 20th century.
Inspect the surface of a copper bed warmer. If the surface is pitted, as in ornate in design, then it may be an antique. Examine the surface for elaborate design work, such as pierced patterns in the copper, not just age markings. These were the kinds made for the wealthy, or the homeowners, not the servants. The more decorative or worn the metal, the older it tends to be.
Check the bed warmer for antique maker hallmarks. These types of hallmarks were often used on silver. Silver bed warmers are almost always of the antique variety, as modern reproductions would not be made of real silver, but modern-age metals such as stainless steel.
Inspect the handle. Most antique bed warmers have old wooden handles made from dark wood, such as oak, which was widely used in the earlier centuries. See if there is a lid. Most antique bed warmers were lidded. Be on the lookout for antique bed warmers that don't have lids. These types are considered primitive, as in not finely crafted, and not ornately decorative; just simple in design for usage.
Examine the shape of the warming pan itself. The pan part of a bed warmer that is enclosed was made in the 19th century, and popular in England. Antique warming pans in Italy and in southern France were sauce-pan shaped, as opposed to thicker, rounder models.
Inspect the design of bed wagon bed warmers. On the large antique bed warmers, there are distinct characteristics that separate an authentic piece from a reproduction. Look for especially large contraptions, like a wooden design frame in the shape of a bed, or bed wagons. Look in the center for a space that would have contained a section for holding glowing charcoal or wood. These old types of bed warmers are distinctly antique and of the Victorian era, both in design and concept.