Chemically Sharpened

Stainless steel swivels are, obviously, made of stainless steel. Stainless steel is an "alloy" of iron, with at least 11% chromium added. Also nickel, small amounts of carbon, and sometimes other elements like manganese, molybdenum, nitrogen, or silicon may be added as well, depending on the grade of stainless used.

I'm not familiar with chemical sharpening. It sounds like a gimmick used to justify an inflated price.

Most fishhooks are made of plain high carbon steel. Some may be made of high-carbon stainless, however stainless steel for something as disposable as a fishhook seems like severe overkill. Also fishhooks SHOULD be able to rust and disintegrate after a few years. otherwise they become a hazard to birds and other wildlife, not to mention humans.

Nickel coating aka "nickel electro-plating" is fairly simple and inexpensive. The hooks are cleaned with several dips in both acid and degreasing solutions, then they're hung on a metal rack connected to a power supply of about 5 volts. The hooks are then submerged in a solution containing nickel compounds, usually nickel chloride plus nickel sulfate, and a current is run through them for a few minutes. This deposits a thin layer of pure nickel on the surface of the hooks.

I'm not certain how bronze plating works. I believe it's a similar process. In other words, electroplating.