Vintage manual wind Longines 18L (add more to comments below)
The Longines caliber 18L was produced in Switzerland by Schild S.A. aka ASSA. This movement was produced as an ébauche most commonly known as AS caliber 1726. Longines finished it as the 18L or 18 L/1.
At the time of this listing, replacement prices were found around $95.00.