I have never seen that. By 13,000, actually 12,600 or slightly earlier they had the correct IIC face plate. I have seen the Pull R2 blacked out on IIC's or IIC+'s that were upgraded with an EQ, but otherwise this is wrong. I have 131XX from 8/84 and it has the correct IIC+ faceplate with the pull deep over the master.
The earliest IIC+'s use the leftover IIC faceplates which were Gain Boost over the Master. These are hard to verify 100% unless they are very near 12,500 and a photo of the circuit boards is available.
908SSP does have a valid point. I have seen some wierd things from Mesa, but I have verified the face plate change over, and who made the actual plates for Mesa.