This lens has a single coating of bluish colour, while my other Primotar 18cm f3.5 lens, that's meant to be mounted on a lensboard for medium/large format cameras. Interestingly, both lenses are Primotar but obviously they are physically different, and it's not just the missing lens barrel. I haven't gotten the barrelless version of this lens to work well on the home brew barrel plus helicoid. The Exakta version is just so much easier to work with.
All pictures below were taken with the NEX-6 and the Meyer-Optik Gorlitz Primotar 180mm f3.5 with helicoid.