This picture is based on the saloon in the South Park City Museum, where buildings from Colorado history have been preserved as an open-air museum.
Back in the boom days of the Colorado mining camps, miners paid with gold dust. Prices would be described as “a pinch of gold”. They greased their hair in those days, so, depending on who was taking the pinch of gold, he might run his finger through his hair first so more gold would cling to his finger. But when the miners wiped their fingers, some gold dust would get wiped off and fall on the floor. Saloons in particular ended up with enough gold dust on the floor to make extra money for the saloon keeper when he swept the floor.
In one mining camp in Colorado, some enterprising miners decided to tunnel underneath the town to collect the gold dust that fell through the floorboards of establishments. Though it really happened, the idea is probably best known today for how it was used in the musical Paint Your Wagon (note that it is rated PG-13 for, among other things, joking about polyandry).