A Puzzling Pelikan

[rocl]

Hi all, my first post here and I am not sure if I have got this in the right place or not.
I Have a green 400NN with a serious crack so I bought a 400 Tortoise "body" that also had a nib, but the photo's on the auction site did not show the back of the nib and I was a bit surprised at what arrived, Here is the front with what appears to be a script nib-IMG_3701.JPG
And here is the back-IMG_3702.JPG
From some research it appears to have a feed from an early M400. The script nib appears to be pushed in further than the logo nib on the 400NN-IMG_3703.JPG
I really like the Tortoise and it is in very good condition, but I cannot remove the nib unit. I have tried soaking in room temperature water for 36hrs but it really wants to stay put. I am reluctant to use too much pressure. I was able to remove the nib unit on the 400NN without much difficulty so I was not expecting this. What should I do? There is no repairer where I live and I would need to send it away to get to one. Thanks in advance.