My 10-blade Summitar is from 1950 and is single coated I believe. Also the Hektor is from 1950 and has the same blue coating.

Still it handles flare rather well, if pushed.

I think the Summitar is one of the better deals out there for fast light-weight screwmount lenses. They're comparably inexpensive and easy to find in quite ok condition. I use my Summitar as much as I use the 50 Asph and have never noticed that the coating would be soft. I don't even have a cap or a filter on it.