The Standard Catalog of S&W 3rd edition says the plastic boxes started being used in 1997, and there are two styles. The early boxes had square corners with a ridge along the edges, and "flip up" latches on the box lid. The later ones (still in use) have rounded corners with different style latches on the tray (bottom) section.
The book also indicates that the 65-6 engineering change took effect in 1997.
If S&W remained true to form on how they rolled out changes, they would have used up the remaining inventory of cardboard boxes as the new stuff was phased in.
Depending on how much they had on hand of the old boxes for K-frames in the barrel length that your gun has, and when your gun shipped, it's possible that if it was shipped in early 1997, it could have been in a cardboard box.
So how much of a stickler for detail are you for needing to have the absolute correct box?
If it's just a "paper or plastic" issue, then odds are good that it came in a earlier style plastic box like this:
They come up for sale on ebay and you can also try and post a WTB here in the classified section.
