There is a body line that starts on the front fender, round on the tip and line fades into the fat fender, the chrome strip is above that line on the 47s and inside of it on the 48s the 46 has the running lights between headlights and hood, no turn signals on the 46-48s Other signs, the 46s have vertical lines in the grill pieces and the running light between the headlight and hood, also have black and red guages. 47s and 48s are almost identical, but for the beltline explained above, some 47s early in the prodcution year had the rectangular running lights in the 46 position.
I would go introduce myself and see what the guy (or gal) will tell you about it. Find out what motor is in it, where they got such a high quality car cover, when they got it, etc. If it is for sale, they will let you know once you have shown a some interest.
It's a 48. 47parking lights were in the same place but the lenses stick out. 48's are almost flush with the bezel like whats on there
I think the top is covered to hide the fact that they are living in it - a little privacy at night, you know? : ) Actually if the car is in Washington state it has only been outside there a short while or it would have moss growing all over it. Go ask.