1957 AU Sixpence - Doubling, Overdate, Something Else Or Is The 7 Standard Issue?

Hi again,
I had an error sixpence up in another forum regarding verdigris / PVC and another punter queried whether there was an overdate on the 7.
I looked into it a bit and it's not an overstamp that I can tell but there is something underlying the downstroke of the 7. As far as I can tell it appears on most if not all other sixpences of this year, but some on ebay maybe don't have this feature. So my question is, do you have a 1957 sixpence that does not have this underlying step?

Wiser heads than mine will be able to tell if it is Machine Doubling but to my eye it is not quite that.

The first picture is from the error coin. The 7 also appears to have a small lump (I ain't sayin' cud!) at the bottom of the right side of the down leg. Also the bottom of the 1 left side looks suspect, as does the 1 in the second picture.

The second pic is from a standard sixpence out of my spares bag.
It has the same left side step on the 7, as well as a small tip on the left arm of the 1 at the top - probably a small cud die chip.

So does your 1957 have the step on the left?