Hi Hoi,
this watch has several well known signs of a fake SM300.
It has 'stubbies' - these are the tick marks on the dial that continue right through the lume patches at the hours to the edge of the dial.
The loops on the 6 and 9 are fully closed - on the genuine dials they are slightly open.
The 'A' in Waterproof on the caseback has a pointed tip. On the genuine casebacks this 'A' has a flat top.
These two pics are from genuine SM300s, albeit recent ones, not vintage.


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