"pre war gustav genschow 10,75x68" http://www.egun.de/market/item.php?id=4307625&PHPSESSID=1c48372950c373727e35fa1e0204049c

what you see here is an ex gustav genschow 10,75x57 with another old stock and rechambered for the 10,75x68, probably completly reworked with a new blueing, imho.
the valuable Zeiss Ziel 6 on claw mount could be old but its also possible it was made new when this rifle was seeing the work bench again lately.
serial number 902 make it the first model whats clearly visible on the front sight. Rolf here have bought the number 905 last year.
http://forums.nitroexpress.com/showflat.php?Cat=0&Number=206900&an=0&page=0#Post206900

lots of high quality pics but the seller dont show the old caliber specification on the barrel. all of you thinking the neuseeland original mauser is to expensive look at the price asking for this rifle.