Posted: 2/4/2026 6:12:19 PM EDT
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Howdy all! I've recently dug grandpa's Seiko dress watch out of my "stack of stuff" and want to get it running again. It's a 7N00-7A49 model quartz. I think it's from the 1990's and wasn't an expensive watch, but I'd like to get it usable. I assume the back just pries off, but I've tried with an Exacto knife and cannot get it to budge. Any tricks or tools I need or does this back a screw off and I'm pissing up a rope trying to pry it off?  Pics..   Pic of grandpa in the Phillipenes circa 1945.  Thanks! |
...behind every blade of grass...
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Just running the 321-491 through Google, it looks like it may be a screw-down back. I would take the bracelet off and use your palm to attempt to unscrew it against. They make a soft "watch ball" for that purpose, too. I would not try to pry it off until you can confirm that it is a pryback case. TONS of Reddit watch subs to ask. Edit: further research says it probably is a snap-off back. Look for a notch in the case back. |
It’s definitely a snap back. The trick is to find the gap before trying to pry it off. It should look similar to this (the gap is near the top): If you can’t get it with a knife and/or don’t want to scratch it up, get a case opener:  
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Just take it to most any jewelry store and they can replace the cell for you for a minimal charge. In fact, many of the mall watch stands can do it. Be aware that the rubber "O" ring on the case back may be deteriorated and should be replaced. |
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Any decent local jewelry store will be able to do it Getting it off is only half the battle. Then you got to out it back together For $30 or less ( About $20 is average for my area ) For that, it is worth subbing out to a pro. To not mess anything up Of they want $50, or more tell them to F off |
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What G_S said.. If it's hard to get the back off it'll be really hard to get it back on without a press. Add to that the size of the crystal and the small bezel and you risk cracking the crystal. I tell people who want to change their own batteries that it isn't hard to do, it's just so easy to screw up. |
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I was recently in the same boat with an older Seiko. Took it to a local jewelry dealer that does watch repair. They did it in about 5 minutes while I looked at new watches and charged me $15. I'm all for DIY but this is one of the cases where it was just easier and not all that much more $ to let a pro do it. |
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I'm glad you got it going. I just wanted to post about RepairTJC online. They have worked on a few of my watches and battery replacements are pretty cheap. RepairTJC |
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"Finally, my brethren, be strong in the Lord, and in the power of his might. Ephesians 6:10 KJV
"Finally, my brethren, be strong in the Lord, and in the power of his might. Ephesians 6:10 KJV