I have no clue when S&W made its first two-tone, but it's been quite a long while ago.
The last ones I know of (before the IL) were 1999 when S&W created two-tone Chiefs Special Model 36s that were actually serial numbered in line with ones shipped in the early '70s. They were cobbled together from parts left over from that era. As I recall there were 75 in that production sequence.
They're gorgeous, and I covet one!