Professional Buttonholer by Singer.
Model number 102878.
To be used with vertical-needle zig zag sewing machines. This is used to make button holes. Comes with 20 different button types. Small and conveniently hand-held. Comes with a lock, size, and placement setting. Instruction manual is included. This product is in great and working condition. Made in Great Britain.
Hallmarked on the bottom.