The problem with rimless gauges Brian and others is that there is no standard as to where on the tapered neck the 1.635 is measured from. It is usually from a certain diameter but, alas, that diameter isn't a standard!

So you can get a gauge that is SAID to be someones idea of 1.635, when it's calibrated on our calibration kit, it turns out to be anything BUT! I trust that you have a calibrated set Brian?

But the offers there!