MILWARDS SKIRT LEVEL "For The Perfect Skirt Line At The Height Of Fashion" - Part D 606 with Box (made in England) and Unopened container of Collins Special Marking Powder (made in the USA). Perfect for your mid-century sewing kit! Instructions are on the back of the box.
I'm wondering if the 7/6 written on the box was the price written on it - Seven shillings and Sixpence.
The level seems to function as designed; it marks a line and the suction cup works (see pics). The unopened container of Collins Marking Powder feels like it's lose and powdery, and not caked up when I shake it, but no guarantees. The box has some marks and wear on it and has been mashed down at some point. (see pics)