Lens Helios 44 Silver 58mm f/2 M39, 13 Aperture Blades! Soviet Lens Zenit USSR. The Helios 44 Silver 58mm f/2 lens is a high-quality, manual focus lens with a maximum aperture of f/2. It features 13 aperture blades, a fixed focal length of 58mm, and a M39 mount.
eBay