qgis - I have a .sid image but can't figure out the CRS

There is a .map file:

OziExplorer Map Data File Version 2.2
Tiritir_2.sid
C:\OziExplorer\Maps\Islands\Tiritir_2.sid
1 ,Map Code,
Geodetic Datum 1949,WGS 84,   0.0000,   0.0000,WGS 84
Reserved 1

Reserved 2
Magnetic Variation,,,E
Map Projection,(NZG) New Zealand Grid,PolyCal,No,AutoCalOnly,No,BSBUseWPX,No

my best guess is NZGD49 North Island but when I use this projection the data from the GPS does not match. Any ideas?

Answer

What about EPSG:27200? The others are more or less locally adopted, but the file info does not name any.

How much offset do you get?