It seems highly unlikely that a wolframite or tungsten alloy would be utilized as a steel for gun barrels. Those alloys are used for armor plate or armor piercing projectiles, and would be much too hard and brittle for barrels.
I remember working in a hot mill where a lot of steel that was used for armor plate or fragmentation (cluster) bombs and grenades was produced. The stuff would occasionally shatter like glass even when it was being coiled up while still glowing red hot. Shards would go right through the sheet steel siding at the end of the mill building. Naturally, it was not a good idea to be near the downcoilers when that stuff was being rolled.
The odds of finding out just where Dan Lefever bought barrels marked Imperial Steel are remote at best. Records from his companies are pretty much non-existent. If one of my Lefever guns is marked Krupp or LLH, then I know. Anything that isn't identified is a guessing game. I have a D.M. Lefever that appears to be a 7D with fine Damascus, and an O Excelsior grade with fluid steel tubes. I'll try to take a look at the markings on them in the next day or so.
