I came across a set of Penny lenses and am not sure what they really are. I have a pretty good idea but wanted to ask of the community what your thoughts are. I set one of the lenses on a shelf (ignore the other chattels if you can) with a Mars Ruby and a Penny Ruby. Those lenses appear to have a fairly uniform hue - purple with some red - and the other is just so much more purple than other two. What is this?