all I can say is now that I see these pix I doubt that it's a Gitane, also doubt that it's a Viner, but I suppose it could be almost ANY brand that sourced frames from an Asian contractor in the late 80s or later. The brakebridge looks similar to a Cinelli or GPM unit, but the dropouts look unlike any I'm familiar with (see those sharp corners on the raised forging?), similar to a lot of known shorty DOs, yet different...maybe they've been modified.
Usually associate that "slot" style BB mech with cheaper Asian frames...

I wonder if it this has an Australian connection?