If I remember correctly gel shield (no matter dichroic (glass) or standard plastic) has a side that conducts and a side that is an insulator. Take a ohm meter and probe both sides, right now I can't remember which side it is that is supposed to face the light and which side it is supposed to face away, but I remember that after you do the conductivity test, the conductive side is what matters.
Righto!
And the conductive side faces the lamp, protecting the plastic behind it-