Ok once you have the year figured out, should be pretty easy since most frames are date coded in the serial number. You may not have the correct decals or remember which ones were used. Remember bikes made late in the year were usually the next years model. So if your bike was made say 1089, it could very well be a 1990 model. You may have to look at survivors and their SN or tiny details in the frame or parts group to be certain.
This list shows you the correct decals for the different year Robinsons. As always a work in progress.