The 800 series hitches were introduced in 1953 for the 50,60&70 models. The 800 was produced '53 to '55. The 800A was produced for a short time in '55 and the 801 was produced from '55 on until the 520/620/720 models came out.
Go to jdparts.com and look at parts catalog #397. There are pictures of all three hitches. The 800 series are all a little bit different but they will all work on A,B,G,50,60,or 70 tractors. I have a '52A that I bought from the original owner and it has a 800 hitch with an 813 integral 3-14" plow.