Sorry to say that your liner above is not a genuine piece, a repro.
Here are the points:
- Sweatband is a repro example.
- A washers are more like Euro/Middle-eastern style. Triangular buckle strap added afterwards.
- There is no such thing as a Firestone M2. Only "Westinghouse" and "Inland" liners made M2's.
The nape strap look original from the photo.
Just my opinion, will let other members to add more info.