In Rugby, James Davies built small engines for airplanes in the 1910s.

-As we see in the figure below of a press advertisement, the vertical rule to the left of the engine, measures 6 inches, about 15 centimeters.

“Press advertisement from 1910”

-The size was so small that its two cylinders had a diameter of only 1.25 and a stroke of 1.5 inches.

-Its price, as showed in the ad, is 5 British pounds with 10 shillings. They also offer a brochure for a stamp.