The Markings were made intentionally. From the council of Elrond, Gandalf tells of his trip to Saruman and Gondor. Gandalf describes what he learned from Saruman:
"The Nine, the Seven, and the Three," he said, "had each their proper gem. Not so the One. It was round and unadorned, as it were one of the lesser rings; but its maker set marks upon it that the skilled, maybe, could still see and read."
Isildur wrote this about the Ring.
It was hot when I first took it, hot as a glede, and my hand was scorched, so that I doubt if ever again I shall be free of the pain of it. Yet even as I write it is cooled, and it seemeth to shrink, though it loseth neither its beauty nor its shape. Already the writing upon it, which at first was as clear as red flame, fadeth and is now only barely to be read
The Ring misseth, maybe, the heat of Sauron's hand, which was black and yet burned like fire, and so Gil-galad was destroyed; and maybe were the gold made hot again, the writing would be refreshed.
This seems to prove that Sauron intentionally made the Ring with the inscription, because the heat of his hand made the inscription easy to see and obvious to all. The first quote says that the "maker set marks in it", so to me this proves that Sauron intentionally put them there.