Hello kashif22041,
Without a name plate, it would be a bit dificult to determine that motor parameters.
I assume that you have searched for a similar motor in the Bühler website, and not found your exact model. Rigth?
First, try to compare your motor with the ones in
www.buehlermotor.com and try to determine the RPM rating of your specimen. If you find nothing similar, try 3000 RPM. After that apply enough voltage to bring the motor to that RPM value. Use a perforated disk in the motor axis and a freq. meter, for example, or an optical RPM meter if you have one. Now you can determine Kv. Kt is aproximately the same number as Kv (in the corrsponding coherent units, of course). It could be harder to determine the current rating, but you can manage to load your motor monitoring the case temperature. Increment load and current slowly until you have some 50 ºC above ambient.
For the gear ratio you'll need access to both ends of motor.
Good luck and best regards!
Edit: As Stefaan said, you may have a little encoder in your motor. It could be used to measure RPM. The gear ratio could also be determined disassembling the gear box, but be carefull on not disassembing the motor itself, or you can demagnetize it. Regards!