The whole internet collaborated to determine what this kitchen tool was.

The mixer with rotating parts was patented in 1856 by Baltimore, Maryland, tinner Ralph Collier. This was followed by E.P. Griffith’s whisk patented in England in 1857. Another hand-turned rotary egg beater was patented by J.F. and E.P. Monroe in 1859 in the US.
Their egg beater patent was one of the earliest bought up by the Dover Stamping Company, whose Dover egg beaters became a classic American brand.The term “Dover beater” was commonly in use in February 1929, as seen in this recipe from the Gazette newspaper of Cedar Rapids, IA, for “Hur-Mon Bavarian Cream,” a whipped dessert recipe featuring gelatin, whipped cream, banana and gingerale.

The Monroe design was also manufactured in England.[4] In 1870, Turner Williams of Providence, R.I., invented another Dover egg beater model. In 1884, Willis Johnson of Cincinnati, Ohio, invented new improvements to the egg beater.

The first mixer with electric motor is thought to be the one invented by American Rufus Eastman in 1885.The Hobart Manufacturing Company was an early manufacturer of large commercial mixers,] and they say a new model introduced in 1914 played a key role in the mixer part of their business.

The Hobart KitchenAid and Sunbeam Mixmaster (first produced 1910) were two very early US brands of electric mixer.Domestic electric mixers were rarely used before the 1920s, when they were adopted more widely for home use.

In 1908 Herbert Johnston, an engineer for the Hobart Manufacturing Company, invented an electric standing mixer. His inspiration came from observing a baker mixing bread dough with a metal spoon; soon he was toying with a mechanical counterpart.

By 1915, his 20 gallon (80 L) mixer was standard equipment for most large bakeries. In 1919, Hobart introduced the Kitchen Aid Food Preparer (stand mixer) for the home.