There is a picture on the wikipedia page for the endowment mentioning a dagger:
I inquired if anyone knew what the dagger was for:
“I know that in Masonry, the dagger is used with the cable-tow. They symbolism is that if you rush to quickly into the “temple” you will be stabbed, and if you go too slow you will be hung. The dagger is placed against the bare breast at the first of your initiation into the first degree.” –User Book1830
There is a photo of the Salt Lake temple sword in the Signature Books edition of “The House of the Lord” by James Talmage.
The picture comes from a Mark Twain book. Mark Twain married a prominent mormon who left the faith, so there is a high chance the image is accurate.
In Wife No. 19 (not the greatest source, but a source) they discuss women bathing naked in water and oil in the temple and cutting holes in the garments over the breasts. I assume that the dagger was used for this. Still looking for good sources that confirm it.