Here's another example that has the factory rework date code on the left side grip frame bottom and the two digits "43" stamped on the left side forward grip frame.
(It was posted by forum member Goring's S&W here: (See post #11 in thread link.)
S&W Factory Repair/Refinish Stampings)
I too recall seeing the added two digits on other examples having the normal style factory rework date codes as well.