I am a 65 year old home owner in Chicago. My 60 year old inline flood control check flapper is 10 ft down in front lawn came off its 60 year old hinge.
The Check flapper is in a 10 inch verticle 10 ft clay pipe. Are there any diagrams
Of these old check flappers.

Because of the age and depth of this check valve I think you may need a pro but first call Mayor Daly's office Dept. of Sanitation and ask if this is their valve and not yours. Can't hurt to try.