Break out the "E" box and I go right to the Eagle Mining Company ingots, another of my favorites. Two sources I have read from claim that they surfaced in 1955; Heritage Auctions in listings over recent years and a Bowers and Ruddy Auction listing from March 1982. Numerous other writings state they surfaced in the late 60's. Fred points out that no truths have ever come forward regarding these; add valuation and a splitting image of the US Mint vignette and regardless of fact, you have highly collectible precious metal ingots in my opinion.
Pictured first is my complete collection, note the slight variations throughout. Most recently I was able to acquire the 998 fine example from Greg, the only Eagle Mining Company ingot I have seen that is not 999 fine.
Individual examples of both 999 fine and the one 998 fine follow.
The next pictures provide hallmark examples for comparison; the first from the Eagle Mining Company, second from the US Assay Office New York, third from the US Mint Philadelphia and fourth from US Mint San Francisco.
As always, anyone have anything to add please do.