There are 5 different versions of this kit. The original issues said "THOR" and "MORSER KARL" on the box (see the history in the attached graphic). These came with railway carrier parts. There were two of these old issues plus one more recent re-issue of this same kit ("60cm MORSER KARL 040 PRODUCTION TYPE w/ RAILWAY CARRIER"). I'm not 100% sure whether the most recent one has the exact same parts, but I believe it's the same as the vintage version.
There was also a vintage version labeled "KARL WITH MUNITIONSPANZER IV." This did *not* have all of the parts in the original kit, as there was no railway carrier, but it also added new parts for the tank, etc. There was also a newer reissue of this version that has the same box art.
Then, most recently, Hasegawa modified the "KARL WITH MUNITIONSPANZER IV" kit to come up with a new kit ("54cm MORSER KARL 041 w/ MUNITIONSPANZER IV aus. F"). This featured a different gun barrel. I have no idea how many parts in this new version are the same as any of the older issues.