The Submariner 5512 was in production from 1959 to 1978. The biggest change to this Submariner versus the previous models: 5510 & 6538 was the inclusion of crown guards. These square crown guards made it exceptionally difficult to use the crown with diving gloves on, so they were redesigned and replaced with pointed crown guards. The remaining 5512 cases were sent to Tudor to become the Tudor Submariner ref. 7928. The early 5512 models were not chronometer certified. But, newer versions were released with a chronometer certified caliber 1560. The ref. 5513 was also not chronometer certified and favored by the general public because it was a less expensive option than its nearly identical predecessor 5512.