How to service a mechanical watch Part 1 AS 1900 in a Rotary watch

I wasn’t able to get the back off. vintage omega seamaster automatic men’s wristwatch for parts or repair. This item is in the category Jewelry & Watches\Watches\Wristwatches. This item can be shipped to United States, to Canada, to United Kingdom, DK, RO, SK, BG, CZ, FI, HU, LV, LT, MT, EE, to Australia, GR, PT, CY, SI, to Japan, to China, SE, KR, ID, to Taiwan, TH, to Belgium, to France, to Hong Kong, to Ireland, to Netherlands, PL, to Spain, to Italy, to Germany, to Austria, RU, IL, to Mexico, to New Zealand, SG, NO, SA, UA, AE, QA, KW, BH, HR, MY, CL, CO, CR, PA, TT, GT, SV, HN, JM.