"It is in most cases still essential to deposit a thin initial layer of copper from a cyanide colution onto both steel and zinc alloy diecastings for reasons already discussed, prior to their being acid copper plated. Alternatively, a thin initial nickel layer deposited from any standard bath is also quite satisfactory on ferrous substrates. In both cases, the thin initial layer is often called a 'strike plate'. (_Nickel and Chromium Plating_)
Punctuation is per the original -- in other words, this is a British book. <g> In American parlance, this initial layer is called a "strike layer." If you Google [nickel "strike layer"] you'll see that nickel is used for the strike on many other metals as well, often under a copper leveling layer, which is then topped with nickel, and then chromium. But cyanide-based copper can also used for strike layers. The leveling layer is sometimes electroless, but more commonly it's copper plated from an acid bath, rather than a cyanide bath.
Top-quality chrome plating, therefore, actually is a four-layer process, even if the first two layers are different methods of plating copper. My limited understanding is that nickel is used for the flash more often than copper in high-volume operations. It's done that way where durability is important and they don't want to use excessively thick layers of plating.
-- Ed Huntress