The Ibanez model ATDS10NT flat top acoustic guitar with tremolo

Although uncommon, I have seen acoustic guitars equipped with tremolo arms before now, or should I say "vibratos" because as far as I can recall these have exclusively been arched-top acoustics equipped with Bigsby vibratos. This Japanese-made Ibanez model ATDS10NT circa 1983 is something else, as it has what appears to be a tremolo-arm mounted into an electric-style floating bridge, which is allegedly "fully functioning". 

This item sold on eBay recently for US $599.