This is from my uncle's estate and I know NOTHING about it. He had some model airplanes but this looks more like a bicycle engine to me. It turns over by hand and has compression. Appears to be in nice shape with one broken mounting tab as seen in the last picture.
If anyone knows more about this then please let me know. The item "Vintage FOX Model Airplane, R/C, Bicycle Bike Engine, Motor" is in sale since Thursday, April 8, 2021. This item is in the category "Toys & Hobbies\Radio Control & Control Line\RC Model Vehicle Parts & Accs\Engine, Exhaust & Fuel Systems\Gas/Nitro Engines".
The seller is "mintpossessions" and is located in Huron, Ohio. This item can be shipped to United States.