Csa Sc. #4 Used (Counterfeit?) From Grab Bag Purchase

Up for inspection is a CSA sc. #4 I received in a grab bag lot. I was hoping someone who has experience with these issues can give it a look and tell me if authentic or counterfeit.
Despite being in poor condition I'm happy to have it, since I don't have any CSA stamps in the collection.
A bit of a personal side note: I attended Jefferson Davis middle school (long since renamed) in West Palm Beach back in the seventies. Thanks!

EDIT: Attached scan was stretched, so I rescanned. Something happened when cropping. Fixed now.

you should check out:

https://www.trishkaufmann.com/csa-fakes

Thanks for the excellent link..... lots of info to absorb.