The Summitar is a truly wonderful lens. Mine is in the 800xxx range, so from 1954 or 1955, fully coated, has no haze and is overall in absolutely brilliant condition - a rare find given the dismal specimens of Leica standard lenses I've seen being sold for insane prices here in Australia. (It came with a Leica iif kit I bought recently).
Lens hoods for the 'tar were squarish (rectangular) and odd-looking but also sell for the cost of a kidney here in Melbourne. It was my good luck that with the camera I bought, I got several original Leitz filters for the Summitar, including a UV which now lives on the lens. Also a light orange yellow I use often, a deep yellow which Ive yet to try out, an orange AND an original red, which apparently is quite rare and highly sought after. These filters recess slightly into the lens front mount and I've found with a little care (which means no shooting directly into the sun, otherwise using as normal) I can avoid flare.
I have yet to test my new (to me) Summitar with color film, but I'll most definitely put a roll or two of Fuji 400 through it when the weather improves and we see the sun again, which I hope will be soon.
Some very fine B&W images in this thread. Master craftsmen/women at work. Kudos to all who posted.