NA-7G.
I don't know the origin of that photo, but I do know that when Irving Klaw shot his images, the first 2 letters were the initials of the model, so IF this is Klaw, whoever "NG" was, I presume that she is the one tied up.
I'd also reasonably assume that Klaw shot more than one photo of this setup (he wouldn't go to the trouble of just one shot.) On the other hand, thanks to the Kefauver hearings, he got rid of most his photos, negatives included. That survives today is mostly thanks to Paula grabbing a bunch of pix & films and storing them.
So while this may at one time have been an entire photo set of 5, 10 pictures, this me be the only one that bade it out of the 1950s. Did he have a model with the initials N.G.? she may be lost & unknown at this point, if this was even a Klaw photo.