You wrote that you received the reply, "the marriage is on folio 1742". I hope you were also given the names of the parties involved, but if not, I'll check for you.
That number is the 'folio number' identifying the marriage certificate. The same practice is used for NZ Birth and Death certificates. To obtain the marriage certificate you need to apply to NZ Birth Deaths and Marriages at the Dept of Internal Affairs and order the certificate. Find the at; http://www.bdm.govt.nz/diawebsite.nsf/wpg_URL/ Services-Births-Deaths-and-Marriages-Index?OpenDocument Scroll down to Forms and select the first one (BDM93) which will open as PDF in Acrobat, print it off, and go from there. On the form I note that a folio number is not required for a Birth Deaths or Marriage certificate, but include it anyway, as it's a good cross-reference.
You'll see from the example of an Intention to Marry Notice that the reference format is completely different from the BDM folio numbers.
Regards, riley
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ELLERKER - Beverley ERY ENG HEALEY - Staffordshire ENG MURDOCH - Wigtownshire SCT PALING - Nottinghamshire ENG RILEY - Flamborough; Cottingham; South Dalton ERY, Manitoba CAN, & London ENG STURTON - Arnold, Nottinghamshire ENG SUTTRON - All, NRY & DUR ENG TAYLOR - London ENG TYLER - London ENG