Russian/Soviet Macka Детский 3 (МД-3), size 3
The Russian/Soviet size 3 Маска Детский 3 (МД-3) was the medium size mask included with the Противогаз Детский Фильтрующий Школьный (ПДФ-Ш) kit. It was made of black rubber and sized for school-age children. This example was made in Ohrenburg in 1989.
Маска Детский 3 (МД-3) = Child's Mask 3 (MD-3)
Противогаз Детский Фильтрующий = "Child's Filtering Gas Mask"
Школьный = "School"
Similar masks in my collection: Russian MD-1A size 4, Russian MD-1A size 1, Russian MD-1A size 5