Brass heads are hollow, made of two pieces soldered together, and soldered to a thin iron shaft. One is loose, and can be removed. A loose clump of solder remains inside.
More expensive andirons of the same style are found with three-dimensional balusters, forged, then turned on a lathe.
See "Iron at Winterthur" #91B for a similar pair, attributed to the Philadelphia region. See "Metalwork in early America" #65B for a very similar form, probably New York City in the first quarter of the 19th Century. See "Antique Iron, English and American: 15th Century Through 1850", especially page 128 #E, although that pair has log-stops. See "The brass book", several pairs on page 44.