It is important to grasp that often it is possible to date items of furniture according to the primary woods used. For example oak pre dates almost everything. Generally walnut follows oak with mahogany imported in quantity in around 1700, continuing right through the 19th and early 20th century. Of course one cannot be dogmatic but the above is a good rule of thumb for beginners.
Coffers are by no means rare and almost every early household would have had at least one. The oak would have been abundantly available locally and an Estate Carpenter would have been able to construct one with ease at at low cost. Often coffers contained a fitted lidded box which was for storing candles.
Look out especially for ‘Sword chests’. Usually quite long to accommodate the sword blade. Often of quite simple plank construction and in demand by collectors.
Beware of early coffers which have been ‘overcarved’ at a later date. Plain coffers were often ‘upgraded’ with later carving which usually is quite amateurish and shallow. Adding a spurious date with initials was a popular pass time in the 19th century and will adversly affect value.