What did Saruman's ring do?

Question

Saruman was a loremaster who delved deep into the lore of the rings. He was of Aulë's maiar, so knew much of making. Eventually he crafted himself a Ring which he hoped would give him power, maybe not as much as the One:

For I am Saruman the Wise, Saruman Ring-maker, Saruman of Many Colours! _{Fellowship of the Ring, The Council of Elrond}

We know the Three help preserve things unchanged, among other things. Did Tolkien ever indicate anything Saruman's ring actually did?

It certainly didn't make Saruman invisible, but he was a maia, and no one else ever wore his ring. Besides, invisibility seems to be more of a side-effect of such rings than an actual power, kind of like a screwdriver can be used as a pry-bar, but that's not what it was made to do.

My best guess is it was an imitation One Ring, in mockery or flattery, which he used to build and control his orcish hordes.

Answer 1

Tolkien made it clear that Saruman did not make a Great Ring (i.e., something to match the Three, the Seven or the Nine) -- much less the One -- in the Introduction where he is denying that LotR is an allegory of WW II:

The real war does not resemble the legendary war in its process or its conclusion. If it had inspired or directed the development of the legend, then certainly the Ring would have been seized and used against Sauron; he would not have been annihilated but enslaved, and Barad-dûr would not have been destroyed but occupied. Saruman, failing to get possession of the Ring, would in the confusion and treacheries of the time have found in Mordor the missing links in his own researches into Ring-lore, and before long he would have made a Great Ring of his own with which to challenge the self-styled Ruler of Middle-earth.

He specifically denies that Saruman had discovered enough to make a Great Ring. And the Great Rings were more than just the One:

'In Eregion long ago many Elven-rings were made, magic rings as you call them, and they were, of course, of various kinds: some more potent and some less. The lesser rings were only essays in the craft before it was full-grown, and to the Elven-smiths they were but trifles - yet still to my mind dangerous for mortals. But the Great Rings, the Rings of Power, they were perilous.

'A mortal, Frodo, who keeps one of the Great Rings, does not die, but he does not grow or obtain more life, he merely continues, until at last every minute is a weariness.

So, at most, Saruman could have made one of the "lesser rings [which] were only essays in the craft before it was full-grown, and to the Elven-smiths they were but trifles"