It would be really weird to have the leads come out of opposite ends like that if they're all for coils within the motor. Just based on the physical arrangement it looks a lot more like a DC motor + encoder/tach than a stepper as H.O. said in the first reply.
The motor is only the top small cylinder, the large cylinder is the gearbox/reduction.
That'd be an ENORMOUS gearbox for that size of motor, especially considering the linear stage is presumably driven by a fine pitch lead screw!
I found the attached datasheet for a motor with a similar part number, 23DT12, on RS's website (couldn't find the actual product), which also looks to be about the right size and shape, and is clearly a brushed DC motor. Note the diagram on the bottom left of the page, which clearly shows the motor in the middle with what is clearly a tach/encoder on one end and a gearbox on the other, just like we see in the OP's photos.
It's possible that the 23HD11 is a stepper in the same body, but Portescap, as they're now called I guess, doesn't list any stepper or BLDC motors with a 23mm body diameter as far as I can see. Neither part number shows up on their website, so my guess is that they're older series, or possibly special order, but most likely the same basic motor.
If the Tango drive is what is used to drive the motor then it is definitely a stepper motor as Benta suggested quoting the manual, maybe a defective stepper but definitely a stepper.
Assuming that's the right version of the manual that goes with this particular stage -- it's entirely possible that at some point they switched between stepper and DC servo arrangements, or that this is a different variation. We also know from OP's
other thread that this is for a Leica-branded stage, so short of more documentation, there's really no guarantee that's the right controller for what the OP has anyway.