When you click the "ACMOCArchives" button on the ACMOC home page it takes you to a page named "Caterpillar Track Type Machines" and then under that it has the heading called "Track Type Tractors -Diesel". When I click on the "Track Type Tractors -Diesel" it seems to be a dead link. The link goes nowhere. Is this posted somewhere eles on the site ? I recall that the page this link used to go to had all the series prefixes 6U, 9U, 1H... and gave the years of mfg for that series.