Diggum,
Actually the price here is quite a good hint that is it treated, I went with the lead glass treatment because it is at the moment one of the most common treatments done to ruby at this time.
By just looking you can see what treatments where applied, or if it was treated.
But only in hand, with magnification/microscope.
Treatments do often leave 'signs', if heat was applied rutile/silk can look molten.
Glass often leaves small spherical bubbles. Or an strange purplish colour in some cases.A
A good article related to lead glass filling can be seen here:
http://www.gia.edu/research-resources/news-from-research/Ruby-Glass_Composites.pdf
Some pictures demonstrate what I'm talking about.
If your lucky it really is less then 1% glass. If your unlucky, less then 2% ruby.
Ok, I'm exaggerating a bit, but you get the point.
I've seen pieces so severely full of glass they give off an certain reaction under the polariscope that no ruby ever should.
What you say makes sense, it can happen also. People copy others cuts all the time.
Every gemcutter in not a designer of cuts. As such he does copy and cut others designs.
The gem testers are no worth much, a polariscope (can be built at home), refractometer and a few other gemmological tools can help you with ID. But you need a reference book; i.e. which materials have what properties.
There are reasonable prices on Ebay, but how good they work I don't know.
Cappy, I'm wondering if it isn't closer to 99% of all gems are treated.
Then the question if if the gem species is routinely treated or not.
And I do accept 2 treatments, heat treatment and oil treatment in emerald.
There's almost no way around those two, so...