556guy,
Jim is right that the plate dates to the Civil War period as the back of the plate indicates. Plates made much later (post civil war) had long loops attached on both sides to attach the belt.
The plate was worn up to 1872 & past that period as many photos indicate.
There are many variations of the plate with some having the German silver wreaths removable from brass plate for easier polishing.
The plate was worn by both officers & enlisted men who wore a saber.
The later plates had small dots behind the eagle instead of the rays.
It is a beautiful plate & a person could make a collection of the different varieties.
A good reference for this & all other equipment worn by the U.S. Cavalry is " Arming & Equipping the U.S. Cavalry 1865-1902" by Dusan Farrington.