You beat me to that Jeff! Welcome Hans-Ulrich. The article that Jeff links to was done recently by the owner of this fine site and it's a thorough tutorial with good quality pictures. It looks like your swingarm is rotted in the same areas as the one in the article.
Maybe worth noting, that this is one area that can be susceptible to rotting on a 1500, especially as it is an area not easily seen, unless the back wheel is out for tyre renewal or whatever.
My '97 had the first signs of rust at the seem on the right, which was gladly noted at a tyre change, by the fitter who knew of this potential problem and made repair accordingly, thus saving me trouble later.
For those of you who change your own tyres, do check when doing them and for those who get them done at a shop, either ask to see the seems whilst the wheel is out or get the mechanic to check and rectify if necessary.
hans-ulrich's picture shows very well what can happen to the swinging arm if left without maintenance.