Hi bro Felix, I am not expert in vintage SM 300. Beside polished case, the bakelite bezel is already replaced. The second hands looks like already replaced,too. The dial looks legit, but wait other experts chime in. No movement and case back picture?
I think it's a nice example - bezel looks like the factory original one and not a redo. Dial and the hands look original to me as well. Case to me doesn't look too bad. If you have a chance to get this you should pursue it pending examination of the caseback and the movement. Prices for these early SM300s (especially with the original bezel) are going up perhaps at an even faster rate than the cal. 321 speedmasters - perhaps partly because of the upcoming reissue piece which looks like a nice facsimile of the original model.
Here is a website with several Omega catalogs from the 1959-62 era when the above watch was current: http://www.old-omegas.com/ This example looks exactly like the Seamaster 300's shown in those catalogs. I can't tell if the bezel is orginal or the good Italian redo. The dial has an original look to it, although I think the hands might be factory service replacements. Other basic diagnostics may be found here: http://www.ebay.com/gds/How-to-Spot-a-Fake-Vintage-Omega-Seamaster-300-/10000000000958528/g.htmlPurchases made through these links may earn this site a commission from the eBay Partner Network If the caseback and movement check out, this could be the cornerstone of a fine collection. gatorcpa
A few things but the zeroes in the bezel are a good tell - Aldo's bezels have a consistent squarish look to it (the circle inside the zero number) while the originals have a roundish look with a variation sometimes in the thickness of the print. This bezel also has the aging of the print in the numbers typical of the original plus has scratches and small imperfections that are not seen in the redone ones.