[jurmous]

I was reading it is based on the part numbers and it is a different number for US bought watches.

If number ends with LW/A you will not have it

https://support.apple.com/en-us/120359

[tylrprtr]

This is correct. You could order a Series 10 from a Canadian source and have a working blood oxygen sensor.

[tedd4u]

Can verify this works. Use reship.com to get a Canadian mailing address and have it forwarded.