Ok - did a little bit of digging and found a few things of interest - again rest assured I'm taking no sides in any of this - just putting information out there.
Below is a short article from the Pacific Marine Review Jan 1921 talking about the Great Western Smelting and Refining Co. - No completely overwhelming information here, but it does seem fairly clear to me that their main purpose was to produce babbitt metal ingots for use in multiple worldwide mfg. purposes. I feel comfortable saying that a company such as GWS&R could have been successful by staying solely in the babbitt ingot business and never getting into any precious metal refining.
I also found a photo of a Ni babbitt ingot produced by GWS&R that looks very similar to the one Carl had with the exception of the word "Nickel."
Finally, I did just a little photoshop work on the image from Greg to try to make some of the letters stand out and I'm confident that the words "Seattle, San Francisco and Los Angeles" are the words across the bottom.
I might be mistaken, but look very closely at the enhanced image of Carl's bar on the right side, I could swear I see an "L" where the L from Nickel appears on the babbitt bar. In fact, an argument could be made that in the 2 areas where it could say "nickel," the bar appears to be hammered and/or altered in such a way as to damage the lettering. The G and R from Great Western Smelting and Refining have been damaged/removed as well.
I really don't know whether it's truly silver or nickel or ? But most of the evidence I came across so far suggests the odds of it being silver are not terribly high.
Still wishing Gollum could pop in here.
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