The crawler can&#039;t be a 1966 model since all Oliver crawler production halted prior to 66. There may have been a few manufactured in 65. If it is small then it could possibly be an OC 46 but these tractors had a 3 cylinder Hercules engine beginning in 1957. The serial no. is located on the right side of bell housing. It is possible it could be an OC12(ser# located front center instrument panel), OC 9 or 96( ser# right side of instrument panel) Landis Zimmerman is an expert on Oliver crawlers and can be reached at 717-738-2573.<!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt=":)" title="Smile" /><!-- s:) -->