Violet add on Lens ?

[Stillwater308]

I noticed a violet add on lens included with a honeycomb and the shade tube included with an Accuracy International rifle case accesories supplied to the Bundeswher . What is that violet ad on lens for ? Thanks

 

[sgtsmmiii]

Possibly a LID filter for optics?

 

[Krazy_jim]

Just a polarized filter I’m guessing, the way the lights hitting it makes it look that color possibly