Is it a new filter or the one that originally came with the mask, if the latter it's probably full of asbestos.
It says "Zivilschutzfilter 68" on the filter. I don't know what that means, the filter has German text on it, but the mask that went with it is Russian. And I don't think they made filters with asbestos, unless you mean that it has a bunch of asbestose in it from being used.