Help identifying my vintage Seamaster

The reference number of the watch will probably be inside the case-back and the caliber and serial numbers will be engraved on the movement. Remove the case-back (or have it done by an expert) and post photos, or use that information for your research.

The crown is not original. Parts may or may not be easy to find, depending on what you are looking for. You didn't provide an introduction or any context about this watch, but if you're thinking about buying it, don't. And if you already own it, unless it has significant sentimental value to you, I wouldn't advise spending any money on it.