Diopter fell out and lost!

[dingadingdang]

So, I just noticed that my diopter (I think that's the right name for the bit of glass that screw in behind the viewfinder?) is gone, I know that it was loose quite often, presumably because it comes undone when I walk and the camera swings a little on my chest.
The question is, does it matter?
what does the diopter actually do?
where can I buy a replacement?
thanks
Craig

 

[glynjones]

Its just a bit of plain glass that protects the viewfinder window. If you scratch this its cheap and easy to replace, rather than the glass that's now exposed

It comes off because of people like me, who remove it and replace it with a dioptre correction lens so I can use my bessa without my glasses on

You can get replacements pretty easily for it
Stephen will likely have some

 

[ClaremontPhoto]

Yes, they do get loose and fall off.

Yes, you can buy a new one.