If it's not obvious the car has an alrm, the way we check at my shop for one is to get in the car, lock it how the alarm should 'arm' (with my mounty, i close the door and hit lock twice in a row, and it arms, most vehicles are like that, or with the door open lock it, then clsoe the door). Wait a few secs, I usually count to 20 or so, then open the door from the inside, if the horn and lights go off, it has an alarm(obviously) if it doesn't, no alarm. If you can't use the handle when it's locked (some vehicles do this so people can't stick something in and pull the door handle outward with a stick to get in) unlock it manually (pull up the lock, push it in or out, etc.) same thing, if horn and lights go off, alarm installed, if not, no alarm installed.