Who assigned the first prefixes K,W, F... ?
 

Hi,

I am currently writing a long article about the history of ham radio for my
website (growing...).
Can someone tell me who :
- What committee or association assigned the first prefix to callsigns in
the middle of 1920's, ITC (future ITU) ?
- On what base (I suppose location) US stations were assigned A, K, N or W
letters and who decided for the other countries ?
- Who currently manage these prefixes at a worldwide scale ? ITU-R (ex CCIR)
?

Thanks in advance

Thierry, ON4SKY
http://www.astrosurf.com/lombry