I see I was mentioned in this post.
To start their are no real or fake checker mirrors, just originals and reproduction Schwinn Sting-ray Racing Mirrors.
I just looked at all my original and repop. Schwinn Sting-ray Racing Mirrors.
Some of the original handlebar clamps were different but all have "Made in JAPAN" stamped, the repop's I have which were the early release have nothing stamped on the h-bar clamp. Knurling were the nuts tighten on original and repop's were different some were deep, others were shallow (smaller diamond pattern) and some knurling were a 1/4" long, as others were less. The H-bar clamp is an easily obtained item from another mirror from that era, could be changed.
I personally know who first repop'd these and there was a first casting and then others to follow. But when these were first reproduced they were made to be very close to exact, of course the "Made in JAPAN" could not be used. The repop's did not have the Sting-ray foil decal attached, the Schwinn Police at that time was in force, copyright infringements as there were many other items, Krate Seat covers was just another. This was before Hyperperformance Pete had bought in to the Schwinn register TM which now Kooleststuff Gary owns.
(Another story for another time)
In conclusion to the question, looking at your Schwinn Sting-ray Racing Mirror I would say it's a reproduction as the Sting-ray Decal on my originals are closer to arm swivel, looks like someone placed it to close too the outer edge.
Just my opinion, I'm not some Schwinn expert, just a hoarder of the stuff.