Philadelphia - 20 to 30 oz Class Ingots
The United States Mint Philadelphia silver ingots in the 20 oz to 30 oz class are the most consistent in shape as well as dimensional height and width of all United States Mint Philadelphia ingots. The varying thickness results in the different weights but all that I have seen to date measure 1.60 inches by 4.00 inches within tenths. Because the molds are tapered, my dimensions are taken from the obverse faces which remain more consistent.
These ingots in the 20 oz to 30 oz class are also the most consistent with stampings. All that I have seen to date are stamped with the Type III hallmark and all are from Melt No. 10. Unlike the 5 oz to 10 oz class, there are no doubled dissimilar hallmarks and reverse surfaces that I have seen to date are blank.
There are about half as many of the 20 oz to 30 oz class silver ingots in the United States Mint Philadelphia Registry as there are 5 oz to 10 oz class silver ingots, only just over a dozen. Within the past two years, by some additional discoveries, I've noted a serial number duplication between the two classes twice as noted within the United States Mint Philadelphia Registry. This will continue to be on the research list for an explanation.