Atropos Antiques has dated this piece to the 1870s.

The back plate still shows the victorian 'kite mark' which is difficult to discern but would indicate the grate was made in the period between 1842 and 1883, by the type of mark I roughly date this piece around 1870.
This is a substantial and heavy item as would be expected, it is 23.5 inches wide and 26 inches in height, 14 inches front to back at the deepest point.
All questions are welcome.
Atropos Antiques has dated this piece to the 1870s.
You can view the stock and full dealer information on the Atropos Antiques Profile Page