Vintage M&B Plastic Tablet Calculation Tray with Rows

This is a vintage blue plastic tablet calculation tray from M&B (May & Baker), a pharmaceutical company. The tray is triangular in shape and has rows and tablets marked on it for calculating dosages. It is likely from the mid-20th century, possibly the 1950s. The tray shows some signs of wear and age, but is in overall good condition for its age and is a unique piece of pharmaceutical history.