I've got a Logitech Fotoman FM-1 which, while it functions, has more flare than it used to have. I assume there was some outgassing which has obscured the sensor somewhat.

My roommate in college had a Wratten #90 that we used to carry, in its original package and when we wanted to view a scene we'd unwrap the foil and hold in the air. In that style, I finally got my own a few years back and I do the same thing, just unwrap to look and gingerly replace it in the foil.

There was a recent discussion that generally concluded these filters are not useful, but when I looked in my backyard, the jasmine bush literally popped out at me while in full color vision mode I barely noticed it from the background.