Newt, I have one of these filters and it is a medium-light orange, factor appears to about 2/3 of a stop with my initial tests. I bought it for use with IR film and get minimal results alone, however combined with a #29 dark red it begins to produce some good ir effect.
As to previous comments about light meters not reading IR, I don't think that's true. A 720nm filter placed over the sensor on my Luna Pro meters give readings within about 3 stops of unfiltered readings, so i expect that like digital sensors there is some IR sensitivity. At least that's been my experience.