Hi Michael, The exact age of your plate is difficult to pinpoint. The back of the plate shows that it (the porcelain body) was probably made in the 18th century, but the decoration itself was popular in the 19th century. Personally I think the way the faces are painted indicates first half or middle of 19th century.
The discrepancy with the age of the porcelain body could be that a blank plate made much earlier was used. I have seen such famille rose plates with old bodies before. So, for me this is likely about mid-19th century.