At the moment we have two conflicting testimonies about what this inscription might be. James B. Bryce,traveling in Armenia in 1876, said that it is inscribed with Om Om Hrum. Following a comment by Andrew West we see that according to Fridtjof Nansen's Armenia and the Near East, it says Om Ah Hum. It is unlikely either of these two travel writers could personally read Tibetan letters, and it is possible that there is more to the inscription than just the three syllables. One clear photograph could easily solve the problem.
Here is a photograph of the mosaic of the Cathedral of Etchmiadzin that is found on the floor of the Armenian Chapel of Saint Gregory the Illuminator. It is reached by a stairway leading down from the Church of the Holy Sepulchre in Jerusalem. On the stones of the walls of this stairway are thousands and thousands of engravings of small Crusader-period crosses.A stairway down the right side of the Chapel of St. Gregory leads still further down to the cave where St. Helena, mother of Constantine, ‘invented’ (i.e. discovered) the True Cross in 326 CE.
So please, come forward with a photo that would be placed on this blog with much thanks. I’m not too proud to beg.