Scotch yoke linkage model steam engine. A scotch yoke mechanism does away with a lot of the side thrust that a conventional connecting rod engine would have. By the patina & look of the brass throttle valve fitting Id guess it was made in the 1920s or 1930s sometime. This engine has the style of some of the old marine engine models that were shown in the early Popular Mechanics magazines around that time.
The engine has wear on it; the main bearings could stand bushings & the eccentric could stand a bushing as well. The engine turns over ok but there is a slightly stiff spot near bottom dead center. The engine runs but it uses a lot of air & doesnt have much power.
Even if its not rebuilt, the engine has a neat look to it & would look good on a display shelf. Its base measures about 2-1/2 x 2-1/2 square & the engine is about 4-3/8 tall. The item "Vintage Antique Early Scotch Yoke Old Marine Steam Engine Model hit miss motor" is in sale since Saturday, November 27, 2021. This item is in the category "Toys & Hobbies\Vintage & Antique Toys\Other Vintage & Antique Toys". The seller is "rowland51" and is located in New Washington, Ohio.This item can be shipped worldwide.