Try turning the watch over and carefully reading the back of the case. Many watch brands actually list the battery number on the back of the case. For instance, the numbers 377 or 2010 are standard watch battery designations. Since the size and shape of the dial does not determine the battery used, for best results take the watch to a local jeweler to have the battery replaced.
Maxell LR626 battery
The Nixon 51-30 watch is an automatic watch and does not need a battery.
my ASPEN watch actually has two batteries. There is a metal plate with a CR2016 battery beneath it but there is a 2nd battery compartment and I do not know which battery it requires.
Take out the battery ;)
CR2032
You take the battery out the watch that's what i did it worked for me
To replace the battery on a Bulova watch, it is recommended to take your watch to a professional watchmaker or jeweler. They will have the tools and expertise needed to properly open the watch case, remove the old battery, and install a new one to ensure it is sealed correctly to maintain water resistance. Attempting to replace the battery yourself can potentially damage the watch if not done correctly.
SR616SW same as 321 and D321
626 or 377
You can find that here http://www.apexbattery.com/watch-batteries-seiko-watch-batteries.html 394 I just replaced one
It probably unscrews. Take it to a jeweler and purchase your battery from them. Most will install for no additional fee.