there are a couple things on the k4900 (19") vs the k4800 (13").
the vertical transistors usually have smaller heat sink on them on the k4800. (not always).
the two larger resistors in the corner behind the flyback (if they are both horizontal mounted its usually a k4800) (if one is horizontal and one vertical than a k4900.)
there are a few other slight things but not so notable.
this is as long as they are original.
i have pictures of both but i haven't had time to put them on our site yet with our other monitor chassis pictures, but next month i will be posting alot more on the site.