Double loupe

Loupe magnifier from darkroom enlarging lens. I modeled it over a Componar-C 3.5/50mm enlarging lens. 

It should be printed with a -0.15 horizontal expansion in order to make the thread work.
Loupe-focus: to be printed in black or light-absorbing material. it allows a -3mm  focusing when you put it on a LF camera focusing screen.
Loupoe-trasp: Print the cone with clear transparent material, it will give you plenty of ambient light nicely diffused when you watch banknotes, stamps, prints or small details.