I do recall a lot of RYRYRYRY test tapes as well as a lot of the "THE QUICK BROWN FOX JUMPED OVER THE LAZY DOGS BACK" tapes back in my Air Force days in the late 60s.
I was taught that the RYRYRY sequence was sent because it used and tested alternate bit combinations in the old 5-bit code used at the time.
Around Christmas time every year the data centers would be streaming and passing along wonderful graphic art work, kind of the predecessor of today's ASCII art and drawings. If the Russkies ever managed to break the crypto codes in the day and decoded one of these long 'art' messages (some were 10ft long when hung on a wall) I wonder what they would have thought of that. 
Lefty