I agree, there appears to be some fund (or larger investor) buying going on.
I have seen them on numerous occasions split orders into weird amounts- so that they appear as separate transactions only to be slowly working at their goal. See 15:04:16 for 10945 and then at the same time for 4055 (15K) and 14:43:14 for 10362 and 9638 (20K). and there are pleny of others throughout this week.
I can't see anyone just lobbing an order for 500k on the table at this stage, better just to bide your time and accumulate somewhat silently.
Cheers D
NKP Price at posting:
64.5¢ Sentiment: LT Buy Disclosure: Held