factory landau roof??

hi
im new and just bought a 1990 25th annv this past fall. going to try to fix it up this spring. the thing that caught my eye was it has a landau roof? and i looked it all over real close and it looks factory. (if not they did a real good job of putting it on) i havent been able to find any info on mustang having that option, just wondering if it WAS an option or special order. I will try to decode the vin when i can get to it in the spring, under snow right now.
any info will be appreciated thanks.
also any good links for decodeing vin for my 1990?
 
yes it a notchback
actually im not fond of those roofs too, but this one doesnt look too bad, and IF it is a factory deal, i may leave it.
where do i post pics of it on here? i just joined today and still looking around.
remember though, i had just got it and nothing has been done to it yet. but i got a good deal for it, $150 and drove it home. drives nice too.
 
ok i finally broke down and dug throught the snow and got the info from the plate.
there is nothing where it says vinyl roof, so it must have been put on.
Im going to try to get hold of the previous owner to track back to see if it was dealer installed.
just thought id fill ya in lol