5 Wire steppers

I have a 50:1 wave drive gearbox that I wish to use but the stepper
motor on it is a 5 wire one and it doesn't seem to have a standard
NEMA 23 frame bolt hole configuration as I have tried a few of my
other motors on it.

I could make an adapter plate up for it but I would like to try and
use the original motor before I do this

How can I tell the center tapped wire on this type of motor as all the
wires have the same ohm reading. I think you can use it on a bipolar
stepper drive if you can find the centre wire.

Any help is much appreciated

Richard.

PS. I ran a search of the forums and came up empty for this topic.