[Milsurplus] BC-312 Crystal filter question

[Hue Miller]

I want to ask someone who's actually used a BC-312 version that has the 
crystal filter.
I did try one, for a few minutes, but it was about 35 years ago. I don't 
recall being very
impressed, but it's been a long time. I recall that I reasoned that a 
lowered load
resistance would make the series resistance of the crystal a more powerful 
factor,
so I lowered it, and noticed no change.
So, is the crystal filter any actual good for adding CW selectivity?
Does the phasing actually notch out carriers?
Maybe I'll have a rematch in the near future!
thanks-
Hue Miller