I was also told by a guy who owns one that...
...another way to spot a fake is by looking at the luminous markers at the 3 & 9 o'clock positions on the dial. Now let me see if I can explain this properly; between the very edge of the dial and the tritium painted markers at 3 and 9 o'clock, there is a thin line which indicates the 15 and 45 minute points on the dial. This IS a fake SM 300. No such line should appear on the real McCoy...according to this fella who owns one. He tells me he was told this by a watchmaker. I will check with the Repair Manager where I work to see if there's any truth in this.
Also ( and I don't know if this is another way to tell or not, but here goes), I've been looking at the vintage Seamaster 300s on eBay for about six months now and I've noticed discrepancies with the numbers on the bezel. On some models, the number ten has a one that looks like this-1. While other models show a one that is just a straight line without the little hook at the top or whatever its called. I only look at non date models with the Cal 552 auto movements. I have heard that this watch was faked quite a bit during the Vietnam War and sold to unwitting soldiers.
Anybody else out there (SteveW62, I'm talkin' to you, man) know if the bezel numbers difference is of any relevance or not? I'd love to know before I purchase one of these babies.
teeritz