Complex sentence: The tests were completed on March 1,1965, and three of the chronographs from different manufactures were still running, but only the Speedmaster had passed without any of the serious discrepancies encountered with the others.
Split into simpler sentences: The tests were completed on March 1,1965. At the completion of the tests, three of the chronographs from different manufactures were still running, but only the Speedmaster had passed without any of the serious discrepancies encountered with the others.