I would agree with the above (without having a actual definitive answer from someone). The reason being is the EX 1 and EX 2 rifles were the trial FN-FALs Canada bought from Belgium to test the system before formal adoption (i.e. figure out if it what they wanted and if there was any specific features they desired or wanted changed).
The Ex1 & Ex2 rifles were received starting in January 1954 (the C1 rifle was in serial mass production in 1956).
The 7.62x51mm trials ammunition used with them ("FAL CDN Ex1" & "FAL CDN Ex2" rifles) was ordered from Belgium (with the rifles) in 1953. It is FN produced and dated 1954 headstamped "FN 7.62 54" (I have several examples in my collection).
I have a factory dummy (un punched primer flash hole) head stamped "DAC^ 54" (neck double roll crimped and holes punched in side body of case)
I have a factory dummy (un punched primer flash hole) head stamped "D.A. 55 +"
I have 7.62 ball head stamped "D.A. 56 +"
I have a factory dummy (un punched primer flash hole) head stamped "DA 58 +" (neck double roll crimped and holes punched in side body of case)
I have a bullet length blank head stamped "DA 58 +"
I have a neck length blank head stamped "DA 58 +"
I have several examples of "EX-" marked 7.62 nato boxes in my collection including the "303 type" 40/50rd boxes as described, and 'EX2" 10 round packets containing 2 - 5 round chargers (ie. stripper clips) dated 1958 & 1959.
"10 CARTRIDGES - 7.62 MM BALL - CDN EX2 - IN CLIPS - LOT 131" packets contain cartridges head stamped "D.A. 58 +" and the chargers are marked "C1 DAQ 8-58"
"10 CARTRIDGES - 7.62 MM BALL - CDN EX2 - IN CLIPS - LOT 197" packets contain cartridges head stamped "D.A. 59 +" and the chargers are marked "C1 DAQ 2-59"
