[BC] RCA phono plugs - How far back?

[Vernon Kuehn]

Help me with history.  In an audio related discussion group someone 
wrote history this way:

"The RCA Phono plug was invented because of Elvis Presly.  The demand 
was so great for Elvis music that RCA invented the 45 rpm record 
player, and to keep the cost down, invented the RCA phono plug as a 
cheaper alternative to the previously used T-R-S phone plug used to 
connect older record players to radios and the new hi-fi sets."

At this point I responded that I hated to rain on his parade, but I 
had been in town for the ORIGINAL parade.

45s came out in 1949 is my memory.  I remember 4-H events in either 
1949 or 1950 where we had music from one of those little 45 record 
players.  What I cannot remember is how old some of the radios were 
that had an RCA phono jack on the back for input.  Someone help me 
there.  One Internet source indicated early 40s as the origin, 
another source indicated maybe in the 30s but neither source offered 
any specifics or back up.

Somewhere in my broadcasting years I remember working for a station 
that had this unique space-saving patch bay where we used single 
prong patch cords that had plugs that looked like they had escaped 
from a manual telephone switchboard.  The  tip and the ring were stair-stepped.

When did the T-R-S phone plugs as we know they come into common 
use.  I am thinking the first one I saw was on a portable sound mixer 
by Peavey used by a church.  And that would have been in the 70's.

How far back does the quarter-inch TRS go, and when did they become 
common in usage?