Page 223 - japanese and korean art Utterberg Collection Christie's March 22 2022

The classic style armor, O-yoroi was developed for use in mounted
combat during the Heian period (AD794-1185) when the bow was
a leading weapon. The large tehen no ana (aperture at the crown
of the helmet), although arising from the method of construction
using riveted plates, was originally used to fix the helmet on the
head by means of the topknot. The large fukigaeshi and hiro-sode
could be presented to the opponent as shields against his arrows,
which service was also provided by the two pendant breast pieces.
All early armors were composed of rows of hon-kozane (individual
scales) laced together with silk braid, and some armors had double
layers of such. Several hundred small scales would be used on the
cuirass alone, either of hardened leather, iron, or alternating those
materials. They were lacquered over in rows, and linked vertically
by silk braid.
The custom of making armors in classic style for both ceremonial
and ritual use dates from the late Muromachi period (1392 - 1604),
but was universal among the daimyo (provincial lords) during the
Edo period (1604 - 1868). Such ritual armors were very expensive
and worn only on certain occasions like the annual passage in and
out of the capital city, Edo, but often displayed on festive occasions
or dates in respect of ancestors. The custom continued even
after the end of the Edo period when armor no longer fulfilled a
practical function.

The accompanied document states Matsuura Hiromu ordered
Nagamura Seisai (1767-1820) and Funakoshi Sadakuni to make this
armor in 1810.