Proofing Rule by Loftus

Differences in the basis of duty payment led to separate developments of the distiller's spirit hydrometer and the brewer's saccharometer.
The former was fiscal duty led whereas the latter was initially developed for process control.
This example is a brewer's saccharometer. The name derived from the measurement of the "saccharin" or fermentable extract in brewer's worts.
This example was manufactured by W.R.Loftus, London in the 1880s.