Nice please explain the acid etching
Hetman, we use acids to oxidize the surface of the steel to add color or patina. Like MikeC says, this was done with ferric chloride which is also used to etch Damascus steel to highlight the pattern in the steel (unetched damascus looks like regular steel).
Milder acids like vinegar or lemon juice are used to bring out temper lines. There's a art/science to getting different finishes,
but the trick is getting nice even finishes and avoiding a spotty or streaky look.
Thanks for commenting,