what is field exitation type of 775 DC motor?
Tiny motors like that are permanent-magnet motors. Available two-winding  motors are much larger and are not widely available because permanent-magnet motors are taking over the market. The resistance can probably be assumed to be nominal voltage divided by stall current. Since the motors are not intended for high performance, the inductance and inertia will probably be difficult to determine. The seller or even the manufacturer may not have that information.