I'm 99% sure it's wind-up' plus I don't even see how the back would come off. Also the face is only about a half inch by a half inch,barely big enough for a button battery, so even though I'm 99 % sure it's wind-up, I'm not 100% sure.
Since, I wasn't sure, I called Seiko, and gave them the number on the back, and they said that it does take a battery, so if you want to cancel your bid, write to listia
yeah, batteries for most womans watches are about as wide as a pencil eraser and thin as a dime. is amazing that they can keep a miniature machine running non-stop for a year plus. watches are a marvel of human achievement. i am a trained machinist and it still blows my mind what rolex can make, and they been doing it for 200 years before computers were invented too, amazing !! and the chinese can copy it for peanuts. hahahaha !!!! nice watch !! .