Vintage SEIKO 6309-735M R, ca. 1977 (from Tim)
6309-7290 or with Dial Markings 6309 735M R Suwa symbol
from Gabriel's article I learned that the size of the Suwa symbol is important. Dials produced later, have a larger Suwa symbol. The dial marking here is a bit dim, but it reads 6309 - 735M R Suwa symbol and it is located at the 6 o'clock marker. If you want to learn more, then please read Gabriel's article. If SCWF had moved that article in the mean time, you can still read an excerpt of it discussing my page here.