[LargeFormat] Temporary alternative to expensive loupes?

[William Wiseman]

I was looking around for a good but less expensive alternative to the 
Schniender/Mamiya/etc. loupes and have been offered a possible 
solution. A friend has a 7x Pocket Optical comparator he purchased and 
is no longer using. the info I have is:

Three element achromatic glass lens system
Eye lens clear lens dia. is 21mm
Clear acrylic base (cover with gaffers tape or paint?)
Accepts 27mm reticles (not needed)

I had used these when I worked as a machinist, many moons ago, and 
thought this might be a temporary solution. And the price is right at 
$20.

Any thoughts/comments?