A gold metallic coating is excellent at reflecting infrared rays (it is not absorptive, it reflects) and gold foil is used on satellites for thermal protection; it is NOT bling. It is also the coating of choice for front-surface mirrors for use with IR laser equipment. Elemental gold is fairly soft as metals go so Roger is correct, be careful if you handle or otherwise contact the surface, and if it is scratched or worn through it is done. Get a new filter and keep it protected or your eyes will suffer.
Harris dual-stage O/A
Lincoln AC/DC buzzbox
Miller 3035 spoolgun
Thermal Arc 185
Thermadyne Cutmaster 52
Angle grinders, vicegrips, the usual suspects
Two hands, tired body, not enough time...