We are giving our daughter my wife’s Watch (she got a new one) but it needs a new band. I looked up sizing that asks what mm do I want in mm. The back though quite small, reads
series 8, 41mm DIA aluminum/ceramic case ION-X GL
iPhone 13, iOS 17
You will want a 41mm band.
You sound knowledgeable and may already know this, but just in case ... here are the instructions to unpair the watch from your wife's iPhone, then pair it to your daughter's iPhone:
Do this first to unpair the watch from your wife's iPhone:
Unpair and erase your Apple Watch - Apple Support
Then do this to pair the watch to your daughter's iPhone:
Set up and pair your Apple Watch with iPhone - Apple Support
Sizing Apple Watch bands
