The Royal .40 and .45 had a two piece front housing like the OS FSR's they copied. Later, the .46 went to a one piece case like the OS SF .46. I am not sure if the .40 was offered with a one piece case or not. Royal did offer a .28 at one time. There may have been a few other displacements, But I have had a .40 and .45 two piece case in my hands.

They were decent engines, but the metal was very brittle and didn't survive crashes well. There was a throttle stop screw that was too soft and caused problems. I replaced mine with an OS part and never had any problems.

turbo