Technical bulletins TB (series). 5-1168-1. Preventive maintenance services: Crane, revolving, crawler-mounted, gasoline, ¾-cubic-yard, 7-to 10-ton. class 3, with attachments. Koehring model 304. with Hilda model K-428 or Chrysler model C-36-520 Ind-9 engine; June 6, 1946.