is this image taken of a Rata, how old could it be if so?
Impressive! Rata would be difficult to age, even if they were cored, so any age would really be a guess. So saying, I wouldn't be surprised at an age of over 500 years for a tree of that size.
It looks surprisingly like the "giant" rata about 15 minutes up the Ngamoko Track at Lake Waikaremoana. If so, it is northern rata and is probably 2 separate root systems grafted together (there are/were two distinct crowns each with it's own primary root). The former rimu host had all but completely rotted away when I was last there 25 years ago.
(JPG format, max 500kB)