To date, in a number of posts, we have looked at ingots with the Mint Of The United States At San Francisco Type I oval hallmark,
and the Mint Of The United States At San Francisco Type II oval hallmark.
In this post we will begin to look at ingots with the Mint Of The United States At San Francisco round dated hallmark, introduced in 1956. This hallmark not only appears independently on the obverse as shown below, but also as a secondary hallmark on the reverse of a number of Type II cast ingots. (The use of this hallmark on the reverse helps with chronological organization as demonstrated on previously posted tables.)
The round dated hallmark was used from 1956 through 1960 when ingot production ended entirely at the San Francisco Mint. It has been thought that introduction of the round dated hallmark ended use of the Type II oval hallmark but recently discovered receipts from 1958 that include both round and oval hallmark ingots proves otherwise.
The only examples that I have seen in the 5 oz class ingots with this round hallmark are all dated 1959.
More to come on the round dated hallmark ingots in future posts and as always, if anyone has anything to add, please let me know.