Hello Louisa...
In a (large-ish) nutshell ... when your Carl applied for NZ Naturalisation he was required to fill in an application form called a
Memorial of Naturalisation. The form asked for his name, age, place of birth, place of residence in NZ and length of residence in NZ. Plus a referee or two saying that he's of good character.
The Memorial is unlikely to mention the 1841 date of birth found in the book
Svenska in NZ (The Swedes in NZ) but we won't know for sure until the Memorial is sighted. If it does mention the 26 Dec 1841 birth-date you won't have to purchase a printout of your Carl's 1914 death certificate (hoping that his parents are mentioned by the informant and that they are the Borge and Petronella found by Ian). If there is a birth-date on the Memorial, supplied by Carl himself, it should be proof enough you're on the right track.
The Memorial should be stored at Wellington Archives as it's mentioned in the
pre-1949 Naturalisations Register, a great big book which comes to us from pre-Internet days. Unfortunately the Memorial can't be found in the current Archives on-line search engine, known as Archway. The Memorial may be mis-filed. It may be lost.
John had a similar experience in the search for the Memorial of his wife's g-grandfather, Walter BRUNGOT. He (quite cleverly I reckon) found the mis-filed Memorial by checking the files of the other men naturalised on the same day as his Walter. Perhaps this mis-filing is what has happened to your Carl's file. The links in my reply (reply no.52) list the available files of the four other men naturalised the same day as your Carl. These files can be viewed at Archives NZ in Wellington.
You might want to start an Archives look-up thread asking for some kind soul to check out the linked files on his/her next visit to the Archives and see if your Carl's file is amongst them.
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To be honest, the last few posts have been a diversion
which might give a few ideas to someone in the future searching for a lost file.
Plus I've learnt that the NZ pre-1949 Naturalisation Register has been scanned and is viewable on-line. No need to go to my local library to check the Naturalisation microfiche. Woohoo :-)
Regards
Beg
PS - if this all comes to naught you may still need to purchase a death certificate printout :-)