How do I identify a two blade aluminum fan

Is there a quick way to determine if I have an original or the replacement two blade fan short of removing it? Any identifying features or marks?
 
My fan will not attract a magnet. I had thought of this but I also was not sure what the original fans were made of. Some things you assume are ferrous turn out not to be. Thanks for reply.
 
Usually I can feel the back edges of the blade .

Original was steel overlapped and the joint can be felt .

The aluminum fans are cast aluminum and the rear edge of the blade will be smooth instead of overlapped pressed sheet metal .
 
Usually I can feel the back edges of the blade .

Original was steel overlapped and the joint can be felt .

The aluminum fans are cast aluminum and the rear edge of the blade will be smooth instead of overlapped pressed sheet metal .

The new aluminum fan I got has the overlap cast into it.
 
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