The serial number won't give you the model, only the date of manufacture. There are some things you can do to narrow down what model it is. On your bike, it looks like the chainguard is a replacement, but maybe it is original, just painted differently. A name will be on there under the repaint, hopefully. Sometimes, if you hold the guard at an angle to the light, you can see the outline of the name. I would also see what color the forks were originally along with the frame. Take the forks off and see what color is on the steering tube, the part hidden in the frame. You can then check the original color of the frame by taking the cranks off and seeing what color the inside of the bottom bracket is, or it can be seen where the repaint is chipped. (Also check the year on the inside of the cranks, 2 digits, they may be a replacement because the sprocket isn't a Phantom) Some of that may be primer color though. Same with the chainguard. On those frames, look for scallops on the top tubes near the front. Every little bit helps.