Jim: Glad to here that!. Chris and I had talked about a series on the Hydralectrics. The only reason I know is. Charles City could keep track of changes made in the units. Also remember they were sold as what they called a "complete tool" or Light line. The numbers then were F-38, F39 &amp; F40. I know there should have been an F-37 for the 66 series of tractors and maybe there was.  Are you going to discuss the cylinders with the fingers? Also when were the first units released? I have a picture of an expermental 88 with the old style sheet metal the K-100 block (has the rear flange like a 60) and that tractor has a hydralectric cable! Also do you know anything about industrial hydraulics (like is used in factories) There is a lot of resemblence between the two. Tell me more, you definately have my attention!! John