This French film is quite different from the movies of its era: mostly French cinema was about comedies (silly or clever, gross or sophisticated) or drama. "Signes extérieurs de richesses" is one of a kind: a romantic comedy with (somewhat) social relevance.
Jean-Jacques - nicknamed Gigi - (the always great Claude Brasseur) is a successful veterinarian. His pet clinic is full of wealthy women, as well as his bed. So, when the IRS sends an average-looking girl (Josiane Balasko) to check his fiscal files, he's not really impressed and even laughs about it, too confident in his accountant Jérôme (the hilarious Jean-Pierre Marielle) who reveals himself to be a crook. Now, Gigi is busy with serious money issues, his clients' pets to care about, and the ugly-but-lovable IRS agent who makes his heart tick...
The characters are really well written, the hero is neither totally an asshole, nor a truly sympathetic guy. Same with the IRS girl shown first-hand as a dragon lady, and who reveals herself a shy, fragile woman seeking love.
Overall, a nice surprise from an otherwise mediocre era for French cinema.