That was not a name, just a statement of "The exact time". It was followed by credit to the National Observatory which synchronized with them.XEQK was also called “La Hora Exacta”.
It was well known to shortwave listeners as the 1350 signal in Mexico City was simulcast on 9555 kHz. I recall the SW signal came in all day long in Texas, and it was interesting to hear the various product and business jingles. The SW transmitter was shut down sometime in the 1990s IIRC.