Although the system approved by King João VI was never put into practice and the old measures would continue to be used for a few decades, the metric system was gaining fans and steps were taken to understand it better.

Prototypes of the measures were ordered from France, which were kept in a wooden safe box, parallelepipedic in shape, with a lid, three brass hinges secured with screws, and three locks, also made of brass, with the respective keys.

The interior is lined with deep-red velvet. The wood is decorated with floral motifs embedded in a rectangle with rounded corners. The base of the chest extends beyond the body, and has a rounded decorative frieze.

A base do cofre é saliente em relação ao corpo e tem um friso decorativo arredondado. A madeira é envernizada. No interior tem os seis encaixes das peças.

Inside the safe box, besides the standards representing the metre, the kilogram and the litre, there were also two different standards that were unrelated to the Metric System: the yard and the pound.