I really can't say other than much of what LV made is highly copied. Fakes are all I ever see and the latches on yours look like all the latches found on most common made briefcases I've seen, but they are signed it appears. The hardware should be better than the average I would expect. I picked up a Hartmann president briefcase once for $30.00 and even posted it on this site. Not many were impressed, saying things like that doesn't sell so good any more and when's the last time you ever saw anyone with a briefcase. I got over $400. for it. I did feel like linking the sale to the post, but just figured I wouldn't. I know what I know and really feel no need to prove it. As for items by Louie Vuitton I'm really out of my element with that stuff and suspicious of any I see.
Only fake LV stuff I've seen are purses mostly and your attaché does look like maybe from the 1970s. I'm on the fence with this one, so you might want find someone who can check it out first hand is all I can say. I'm hoping it turns out to be a score.