Opus Antiques has dated this piece to the 18th Century.

There is a small repair to the top corner above the M.
It measures 23.5cm l x 3.8cm w.
Corsets were called stays prior to 1830 and antique treen stay busks were flat pieces of wood,( could also be made from horn, ivory, metal, baleen or other materials), which were inserted into long pockets at the front of the stay/corset. Many were undecorated and were purely functional to flatten the stomach of the person wearing it. They must have been fairly uncomfortable - difficult to bend down!
The decorated ones were inserted into small pockets at the top and the bottom of the front of the bodice. That were decorated with geometric patterns, chip carved decoration, hearts. Sometimes there was a message carved or a date on the back of the treen busk.
Opus Antiques has dated this piece to the 18th Century.
Antique treen, boxes & decorative georgian items
You can view the stock and full dealer information on the Opus Antiques Profile Page