References

• Spring balance, Salter No. 2 Improved These scales represent those used by the public, on post office counters, and in mail exchanges. The conversion of individual items of international mail liable to postage due would be the reason why metric scales were used in the Mail Exchange Branch in 1942. Tax markings are known in 'centimes', the UPU unit of currency conversion. Source: Spring balance, Salter No. 2, metal, Salter, England, N.D. 2018, Museum of Applied Arts & Sciences, accessed 22 October 2018, <https://ma.as/162205>