The invention of the balance spring in 1675 made previous movements obsolete. However, owners treasured old cases and wished to conserve them. As a result, many Blois watch cases were either fitted with updated movements or converted into snuff boxes. Many backs and covers were preserved for their beauty alone. The present box was mounted, around 1750, from a magnificent mid 17th century watch case. We have seen magnificent Blois cases with later watch movements by Webster, Leroux, Pyke, Fromanteel and Berthoud. The artistry and rarity of these cases unquestionably warranted the expense of commissioning a special movement for them. Ferdinand Berthoud?s registers, from the second half of the 18th century, record that a client requested that Berthoud fit an old enamel watch with an updated movement, in yet another example of this phenomenon.