Whoever wrote the "did not appear on original coils" must not have looked at very many, or at a still-legible end frame. I assure you it is there, unfortunately you have to squint to see mine underneath 55 year old crud (I very carefully did NOT try to clean it off due to the apparent fragility of the ink or paint). If you inspect it under magnification, the lettering is identical to service parts, for a very good reason - same supplier did all of them. I researched and contacted the OEM many years ago, verified who they were and what they supplied (this was laborious, before the internet and Google heyday, when you had to read things and make phone calls). Rochester Division of A/C (Rochester NY) stamped the coil date and the part number likely when they received the valve assembly from the supplier before valve installation and shipping. From all of my research, they were batch built, as there seems to be a small date sample from the originals I've ever researched. I have two NOS "service" coils, and at least one other original (other than this one) that all have identical part numbers and info.
If you remove the printing as specified by whoever suggested it, you will be incorrect in my honest estimation. As usual, just my opinion -
Regards,
Steve
P.S. I should have added you should leave the end frame part number, and remove the reproduction GM number from the side and restamp/ink it. The GM number they applied looks far worse that than the OEM part number on the end of the coil frame in my view.