It is a pressed on back - firmly pressed on, only to be removed for servicing.
First remove the band, you will have an easier time looking all the way around the case for the slightest crack/opening and you won't stupidly apply torque to the band whilst trying to find leverage against the back.

You may find the back overhangs the bezel at one end or the other, which make prying the back off an easy job. Otherwise... you may have to take something really thin like a straight, single-edge razor(window scraper) - push it straight into the crack(don't twist or pry), pull out and move around the case, repeat. Once you do it in 5-10 spots, you will find that it has leveraged the back enough that you can use a regular sized case knife.
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Sales of vintage LED, LCD, analog watches,
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