Are these complete fireplaces or loose parts?

Mostly loose hearth ironwork. Baskets, grates, fire backs, andirons and fenders make up the bulk of what is listed, and each is normally sold on its own or as a pair. Complete cast iron fireplaces and surrounds do come up, but they are a minority. The word surround appears in only a handful of titles.

What does a fireback actually do?

It sits against the back wall of the hearth, shielding the brickwork from the fire and reflecting heat back into the room. It is the oldest cast iron form in the domestic hearth, in use from the 16th century. In listings, firebacks are sold on their subject rather than their size. Royal crests, a lion and unicorn, a passant guardant leopard, a Tree of Life and a Black Forest scene all recur.

Can I trust a date cast into the iron?

Not as a date of manufacture. Revival casting carried old dates for a very long time, and one sampled fireback bearing the initials CR and the year 1635 is dated by its dealer to 1930. Dealer dating across the category runs from 1700 to 1940. A large share rests on the words Victorian or 19th century rather than a specific year.

Where were most of these made?

English is by far the commonest origin named in titles, well ahead of anything else. French pieces are a distant second, and French-attributed pairs of dogs are sometimes listed as chenets. German, Dutch and Italian examples appear singly.

Which pieces sit at the top of the range?

Complete Victorian kitchen cooking ranges. They occupy the whole top of the category, one running to a double oven, another still hung with its brass rail and pots. Below them come the very large and heavy pieces, inglenook baskets and monumental plates, and grates or fenders carrying brass. Miniature surrounds and salesman's samples sit at the other extreme.

How often do these come up for sale?

Around thirty-two pieces a year on Sellingantiques, from a pool of ninety-four dealers who have listed in the category. That means most of those dealers have handled only one or two. Hearth ironwork is something they pick up rather than something they stock in depth.