On Lefever guns the SB&Co (Sanderson Steel) a Sheffield, England, company, stamp many times also had a diamond or rhombus shaped stamped near the SB&Co stamp. This may not have been a Sanderson trade mark as it has also been found on barrels marked LLH. SB&Co appears in the Syracuse city directories of the 1880's.

In the 1880's English exports in the gun trade to the USA started a steady decline. SB&Co had the foresight to set up a plant here. This allowed them to avoid the disastrous fate that would hit other British firms with the McKinley tariff of 1890.

Here is a history of the company.
http://www.sandersonsteel.com/200_years.htm

I do not know any Lefever guns with "Crown Steel" on the barrels, but there is always the exception when it comes to Lefevers.

Pete

http://www.damascus-barrels.com/Movie.html