The Antique Partnership has dated this piece to the Georgian era.
A good smooth working lock by Barrons of London. Original key. Flush military brass side carrying handles. Original brass hook and eye retaining catches to the front. Original butt hinges to the lid. Central lid cartouche with the owners title and No2. A clean interior with the base baize covered.

There are two candidates for the original ownership. I believe The Honorable Hugh Primrose Lindsay 1765-1844 is the most likely. Son of the 5th Earl of Balcarres. Royal Navy Captain, British East India Co Director and Chairman 1826/7 MP for Perth Burghs 1820

The other...The Honorable Charles Hugh Lindsay 1816-1889 British Army officer and politician Son of the 24th Earl of Crawford and interestingly sitter in 7 National Portrait gallery paintings.
The first candidates lifespan fits the age of the box more precisely.
The box was obviously used to contain important documents and/or valuable items.
51.5 cm wide 33 cm deep and 23 cm high.
The Antique Partnership has dated this piece to the Georgian era.
You can view the stock and full dealer information on the The Antique Partnership Profile Page