It honestly looks like a leftover IIB face plate. The Pull Shift on the bass knob and Pull R2 look silk screened.
As with anything Mesa, just because it's 15,202 does not mean it's later than 15,113 etc. I don't think they
were perfectly chronological with serial numbers. As George stated, Mesa did not waste anything. I'm sure we could get
a better understanding if we had the codes on the side of the chassis and the transformer numbers.
Lastly, I do know for certain that if Mesa needed a face plate it did not take them long to get one. The face plate
company was in Oakland. Maybe they used the wrong artwork for a single run.