My Rolex 1500 case a replica ??

[Wintersun]

I have a Rolex Date 1500, with 1570 movement, circa 1972.
There is something thats been bugging me for a while though..
the lug shanks on the case look different on each corner.
Thinner on one side ever so slightly, pics follow.
So i was wondering why, do others have this problem ?
Or is my case possibly a copy ?

Between the lugs i have the correct model number and serial numbers.
although very faint.. is that also correct to have faint stamped numbers ?

I need help on this, as nobody seems to know the answer.
Thanks in advance.