RRC Numbered Radiograms
Radio Relay International (RRI) has their own set of Numbered Radiograms. These are similar, of course, to the ARL Numbered Radiograms we routinely handle. The message check will read "RRC" in front of the check number. More information regarding these messages, as well as a link to the Reference Chart, can be found here.
As to the legality of these messages, it is my opinion (not necessarily that of COTN) that we should handle these messages the same as we would an ARL version. I believe the coding is for efficiency and accuracy of transmission and relay, not to obscure the intended message. The message numbers themselves have been worked to be more compatible with ARL, but they do have additional message numbers.
Like the ARL version, the RRC numbers are spelled out on the radiogram. And when being passed on the air, always spell each number (i.e. RRC SIXTY I spell Sierra India X-Ray Tango Yankee SEVEN I spell Sierra Echo Victor Echo November.)