Hello 
As you know well, in case of International Morsecode,
the code of 8 dits ........ or di-di-di-di-di-di-di-di
is the code for "correction".

On the other hand, in case of Japanese Morsecode (WABUN), 
the code ...-. or di-di-di-dah-di
means "correction".

I was taught that the SN prosign should/could be sent at the start of a transmission to indicate that the previous incoming message had been correctly copied.  "All correct," in fact.  I do often use it, in fact, as in "SN 2E0LUL DE G5VZ RR... etc"

If I am wrong, I will be pleased to be corrected!

73

Chris