Let me add one small point to Drydock's post... While it is very true that the Officer's Pattern 1851 Eagle Belt Plate had the integrally-cast wreath and was gold washed, most of them fit waist belts that were 1-5/8" wide. These belts were, mostly privately purchased by the officers. They were often made of thin leather, doubled over in thirds length-wise, like a business letter, and stitched in either straight or fancy patterns. They didn't wear well, especially under field conditions. The Pattern 1851 Enlisted Belts, waist, saber, etc., had the wreath silver and separately applied. These belts are 1-7/8" wide, made of a single thickness of heavier leather, and because of the way the belts adjust you can't fit the wider, heavier belt to the Officer's plate. As a result, at least in the field many officers wore the wider enlisted belt, with the silver wreath belt plate. Personally, I think the silver wreath is fancier. Modern-made Officer's Belt Plates are obviously simply polished brass, not gold-plated (unless you have a jeweler who does gold-plating...and have the dinero to match!!).
Your obdt servant,