Hi, I also had the same question today, trying to find OM23221ARD schematic.
OM5569 in Jonathan's post is not the right one. It is a different ref board. It is using the same NT3H chip though.
The best article I found for this topic is this:
It doesn't give the schematic, but it gives the pin mapping, which is sufficient for my need.
Dear Gordon Margulieux,
Hope you are doing great, please check the following link this are the schematics available I know this are other evaluation board for NTAG i2c but maybe you can use them as reference.