Bühler and Indrāji found this inscription carved on the side of the mouth of the spout of a watercourse on the road that goes from Kathmandu to the Residency near the Rānīpokharī. Their drawing was used by later scholars who could not find the inscription. Saṃvat 45 (?).

LXXXVIII Ancient water Tank Inscription
Regmi, D. R. Inscriptions of Ancient Nepal. Vol. 2. New Delhi: Abhinav Publ, 1983: 53.

The bright half of the month of Jyeṣṭha, Samvat 45…by the favour of the illustrious Aṁśuvarman, this conduit has been built by Vārtta Vibhuvarman for the increase of his father’s spiritual merit.

Other versions
Bühler, Johann Georg, and Bhagavānlāla Indrāji. 1885. Twenty-three Inscriptions from Nepâl, collected at the expense of H.H. the Navâb of Junâgadh : edited under the patronage of the Government of Bombay. Bombay: Printed at the Education Society's Press; p. 8.