Not an exact date, though it's probably in the archives of the Canadian
Coast Guard, my employer at the time. Hey, I worked at Halifax Coast
Guard radio from 1977 until 1995, 18 years at the one station. We
handled a number of SOS calls on CW and were able to save lives some of
the time (not always. alas). But with trained operators on both ends of
the signal path, CW was pretty much always an easier go than SSB. And
SITOR was pretty much a joke. Half the ships couldn't get it going.
INMARSAT is what put CW out of business in the marine industry. And a
nasty solar flare or two could put INMARSAT out of business. You pays
your money and you takes your chances. I'm not sure that a ship equipped
with a complex satellite radio with a lot of moving parts and a
technician is all that much better off than a ship was when they were
equipped with an MF-HF CW and SSB radio station and a radio operator who
was also a trained technician. All is well until something breaks and
the nearest part is 500 miles away over water.
CW was still in use for a some ship-to-shore work when I retired in 1995.
When I went to the high arctic in 1964 it was our main means of
communication with the south. We eventually converted that to RTTY and
SSB, but neither was really as effective as the CW that preceded.
Now, today, we have such things a PSK31 to do much of the grunt work.
That will work as well as CW in most cases, I find.