According to an Ithaca Service Manual form the 1980s, the Perazzis which they imported back then were built with heat-treated allow steels, unsuitable for case hardening. They were given a "FAUX" case coloring by chemicals. This involved heating the part to around 200 F & then daubing or striping it with Cold Blue. I'd sure hate to pay $4K for that though. One can do a batch of them, themselves for the price of a bottle of Cold Blue.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra