Antique Chinese Repousse Silver Lock Plaque, 7 3/4" wide

Priced in Mexican Pesos.   CHINESE repousse Silver LOCK Plaque, 7 3/4" wide and 6" tall.
There is controversy as to what these repousse silver plate were designed for.  The information that accompanied this one says it is a "Ceremonial Breast Plate, 15C".  Tooled silver, worn front and back.  Showing that the owner was a member of the Imperial family holding the rank equivalent to Colonel.
It also states that this is "Tooled Silver".
Here's the problem with all this information ... 
1st: the silver process uses here is called repousse" hammered from the back side into a wooden mold.  Tooled is another process.
2nd: This couldn't be from the 15th C. since at that time, silver was not a precious metal and the item would have been cast, weighing 3 or 4 times the weight of this piece (which is 2.33 Troy Oz.)
3rd: Pieces like this, with the rectangular slot in the top, are known as a lock plaque which goes over a protruding lock fixture in order to secure a pad lock.. it is called a Lock Plaque.
So, take my opinion or the information that is provided on the little yellowed piece of paper that comes with this piece.  I cannot find any mark on the silver to know its' content.  
Normally China used 80-90% silver content.
VG condition, beautifully patinated.