Spring Scales were used to calculate the monetary value of large numbers of coins. They were used by banks, post offices and businesses.The spring scale was invented by Richard Salter, a British balance maker around 1770. The spring scale, as the name implies, measures the pressure (or the tension) exerted on a spring to deduce the weight of an object.
You would place a coin on the scale, and note the weight of the individual coin. The value of larger numbers of coins could then be calculated by placing them all in the metal pan, dividing the weight of one coin into the total weight of the larger number of coins, the resulting number then being multiplied by the value of the coins to find out the total value of the coins.
For instance if you set the scale to zero and weigh a new penny it should weigh 2.5 grams and so 2 pennies should weigh 5 grams etc.
In the 19th century, portable suspension balance scales were used to weigh coins and in those days it was not uncommon for the value of the gold in a coin to exceed the coin’s stamped denomination. These antique scales, which could be hung from the nearest hook, were designed to fit into metal or wooden cases, including their brass pans and cast-iron or lead weights.