Brand: Unknown (French military issue). Material: Unlisted (feels like 100% wool). Notable Features: High waist, button fly, reinforced seat, pleated front, suspender buttons, Mitin treatment tag. Decade of Manufacture: Likely early 1950s (see Research Notes at bottom).
Vintage Tag Size: Unknown (no size tag). Leg Opening: 8.5 inches. That's a misunderstanding Mitin was a mothproofing treatment and "Mitin Antimite Définiti" roughly translates to Mitin Permanent Moth Protection.
The tag does help us, however, as Mitin treatment was less common after the early part of the 1950s. I'm saying early 1950s on these because to my eye they appear to be made in the transition period between World War II and the cold war. The reinforced seat is more 1940s than 1950s, but things like the suspender buttons look more like 1950s changes.