[Abominog]

Check these out: http://www.apexgunparts.com/zrak-on-m59-scope-w-case-yugoslavian-very-good.html

It's not for the M53, but it DOES fit the Lafette, has 3.5x magnification, are in pretty good shape, and are inexpensive. Take a look.

 

[DanG]

sight

As someone that recently purchased one of these, they are great. However, the reticle is sideways as mounted on the Lafette tripod. If you're going for a display ( as I did, it's sitting in an Armor museum now), it's work great. If you intend to use it for shooting, don't be surprised when the graduations are left to right instead of vertical.
The mount fits right into the dovetail nicely and looks great.
Hope this helps,
DanG

 

[Abominog]

This makes me question what the Yugos did use. After all, they made the mounts on the Lafettes, so one must assume they had optics. One could argue they were going to use surplus German optics, but I have a hard time with that since the Lafettes are far more durable than the optics.