The stem is made of ebonite, material that is traditionally used in producing of smoking pipes.
Rather than following CIA orders, most used whatever funds they received to carry on the work they had already started, and often discarded the advice of the Agency handlers...[A] first-rate book
It was discontinued after the design change around 2013
If you own one of those models, its simply a matter of purchasing the FLT420B filter from Amazon (currently out of stock) or directly from Guardian Technologies for $40
Because they are strong and reliable, they help keep papers safe from bending, tearing, or getting damaged during storage and shipping
Ps, you can cut the handle off the brush while its still wet and leave it in the can for future spot priming