This is most intriguing indeed. The CAST STEEL stamp was used exclusively for the tool industry. Quite literally hundreds of thousands of tools were stamped thusly, most between 1800-40. Everything from hammers, axes, saws, chisels, etc, to scissors, thread-cutting dies, button hole cutters, etc, etc.
It was used to advertise the fact that they were made from the highest quality steel.
As a material, it didn't exist until the 1780's. By the 1840's, it was assumed that all tools were made of cast steel.
The WARRANTED stamp was mostly used for tools, but sometimes carried over to other branches. For example, English flint and percussion gun locks meant for export. But pardon my digression here.
You have an excellent eye for letter fonts. In museums, that's often the best method to date an artifact. It's subjective, but after looking at enough examples, one gets a feel for it. Myself, I would have perhaps gone a tad earlier, 1820-40.
I don't believe the N-YORK was a test strike, simply because it was on silver. It would be like lighting a cigar with a 20 dollar bill when a 10 would have worked just as well. (Tongue in cheek here).