SIG P232 slide finish

[Zundfolge]

So newer P232s have the "Nitron" finish, but does anyone know when they switched from blue to Nitron?

My P232 could use a refinish to the slide but I don't know which finish is stock.

Mine is date marked KJ (so 1998) and looks like blue to me.

Looks blue to me, but I don't know what Nitron looks like when it wears.

 

[usp9]

My KH P230 looks just like my AD P232. If it has changed it's been since then.