First-price sealed-bid auction. Rather than an auctioneer calling out prices a silent auction is all done on paper (hence the 'silent').
It's called a closed auction and it's not exactly on paper. It is closed because not everyone can come or find out about it. And most ITTs will contain details of the person and their willingness to participate. The first-price sealed-bid auction is called so because many people do not know the initial price, but after receiving confirmation they will know it. And only then is there a tender among those who have agreed to participate further in it. If not, then those who have agreed to all terms get access to the auction by tender.