Just bought a seamaster 600 from ebay. Was a little apprehencious as there were no photos of the inside however it appears to my amateur eye to be genuine and in good order. It would appear the crystal has been replaced as there is no omega logo on it as well as some minor signs of aging on the one and two o'clock hour markers. Here are some photos: http://imageshack.us/a/img209/4380/img1914wb.jpg http://imageshack.us/a/img152/429/img1915b.jpg http://imageshack.us/a/img267/9243/img1916qs.jpg http://imageshack.us/a/img571/5048/img1918jf.jpg http://imageshack.us/a/img203/9742/img1919m.jpg http://imageshack.us/a/img62/8987/img1920bp.jpg http://imageshack.us/a/img189/6527/img1921bb.jpg http://imageshack.us/a/img560/4096/img1922fn.jpg I paid £235 for it. I think I did well for what I paid? What was the difference between the 600 and other seamasters?
At US$350 or so, I think you did OK. Watch looks to be all original and don't count out the crystal until you examine it with a loupe. The symbol doesn't always show up in photos. There may have been engraving on the back that was removed, I really can't tell from the photo. The "600" designation has to do with the caliber 6XX movements inside. These were considered the latest thing in the early 1960's. Nice looking watch. gatorcpa