Help with this funny vertical thing

[David 11084]

Hi, I have Fodis/Fokis rangefinder for my 1A. A previous owner has fitted a red glass to the rangefinder window-supposedly to improve the contrast. It works ok but I am reluctant to remove it and try without-this is my preference.
Can anyone shed some light as to why it would have been fitted? Any suggestions? You do get some funny looks when using it!
David

 

[colyn]

Usually red or orange contrast filters are used with rangefinders because the beamsplitter has gotten weak and is difficult to see both images.

 

[kbg32]

I'm not sure I am understanding your question, because you gave the answer in your post. -
"A previous owner has fitted a red glass to the rangefinder window-supposedly to improve the contrast."

 

[Luddite Frank]

Leica offered little orange slip-on filters for the RF windows of the II & III series cameras, to improve contrast in the RF.

They are known by the codes ORAKO and OKARO.

They have been in the Leica sales catalogues since the 1930's...