Generally reserved for marking the reverse of large plates of silver prior to shearing, the Type III oval hallmark founds its way onto at least two cast ingot obverse surfaces. I recently acquired the example pictured below, #37, which now makes a grand total of two that I have ever seen, both are in my collection.
Not only is the Type III hallmark a rarity, #37 is the lowest of all serial numbers I have ever found on these 25 oz class cast examples. Ingots from this class that I have examined or have good information available, are from a limited number of melts or lot numbers. Lot 1, Lot 2, Lot 164 and Lot 178 have been identified to date. #37 is from Lot 1.
The photo below shows the difference between the Type II and Type III oval hallmarks.
A photo to show the difference in size between the 25 oz class and the 5 oz class ingots.
And the final photo shows the use of the Type III hallmark on the reverse of a sheared plate example overlaid on #1267.