Greetings, I am new at this but here is information on this watch. On the dial is "Seiko Beauty" and "Diashock 17 jewels Japan" Markings on metal are k18 in a box. A #5503. Inside of case has a flag, 750 inside a diamond # 098623. 17 jewels Seikosha.
I have not been able to find this "Seiko Beauty" model anywhere. I have found other Seiko watches that look just like mine but they have a different Seiko name on the dial, not "Beauty" Also,none of the watches on Ebay like this mention 18k. I am wondering if one of the marks indicates plated maybe over chrome.
It's a date calc for Seiko's. Normally the 1st diget of the serial number is year so your's is a 0 so 1970/80?! and the second the month so yours being 9 = September. You just need to know the decade but the date calculator link might tell you that.
In the early 1960's there were a few of the high end Seikos (GS, Chronometer) that used 18K cases. Since the movement is marked Seikosha I would think it is pre 1964 (someone with more knowledge correct me if I am wrong)
Nice watch (and I assume it is a womans watch based on the nomenclature of "beauty" on the dial)
The watch is from the very late 50's or more likely the early 60's as others have indicated.
The case is solid 18K gold. The Japanese flag and 750 in a diamond indicate the purity of gold in the official Japanese rating system. If the value was 1000 it would be 24K, if it is 500 12K gold. Below is a quick table with the values.