I learned something this afternoon: my digi is woeful at manual focus!
But I was able to get a few shots.
Set my camera to ISO 80, about 64mm equivalent, manual focus set to infinity, and in camera BW (after the first two color shots).
The filter I used is a Walz Type A - daylight filter. 1950's vintage, sized 40.5mm (I got a set of filters and a hood I use mainly on my Jupiter-8 lens. I got red 25, orange, med. yellow, yellow-green, and the one I used today, and a blue one marked "flash").
my digital camera does not have filter threads so I put the camera on a tripod, framed, set the self timer, held the filter in front of the lens and tripped the shutter.
The filter was about 1 stop slower than the photos with out; 1/320 vs. 1/640.
It appears to me to have a bit less change of contrast than the orange and the photos look to me to be very similar to the yellow-green and the med. yellow.
I had a red 25 filter with the other filters until I got to where I was shooting and discovered it was not in the stack but at home on my J-8.
I don't think I will use the type A for BW film but I can see using it with color film as a warming filter, I suppose.
I have a small Kodak box marked "Kodachrome type A/daylight filter" which was what I intended to use for this little test but that box turned out to be empty.
This exercise may not translate directly to your Leitz filter but I hope it will give you some idea of what to expect.