Tank idler wheels?

[Luke R]

I was given a tip off about these wheels on ebay.
http://www.ebay.com.au/itm/231516654...%3AMEBIDX%3AIT

At first I thought they were idlers off a AC Sentinel tank but I haven't found any images of AC tanks with these style wheels.
Ive found many pics of the idlers with four holes a couple of images with eight holes but none with six.
They are very close dimensions to that of idlers of Lee,Grant,Sherman chassis, so are they a rarer style of idler wheel in the fairly large collection to suit these tanks.
Or is it just a fluke that the dimensions are so close and they have nothing to do with tanks at all?
Anyone have any idea?

Luke.