Is it unusual for a very late 70's 5513 to have a Serif dial?

[fizz]

Everything I've read (here, 5513mattedial.com etc.) suggests that a late 70's 5513, specifically one from 1979 (serial no 595X), should have a Maxi 2 dial. In some rare occurrences I have seen versions with either Maxi 1 or 3 as well.

However, I came across this 5513 which seems to have a Serif dial. These are commonly found in the mid 2.5 to 4 serial numbers, so I find this a bit odd.

Is it possible that this is an anomaly that was actual made around 79 but using an older Serif dial instead of the period correct Maxi 1/2. I'm assuming it's not a service replacement because that would have more likely been fulfilled by one of the later Maxi's (4/5) or Gold surrounds.

Nothing about the watch indicates there is anything seemingly wrong about it. In fact, it ticks all the right boxes (serial number, patina, bezel, pearl, matching hands, strong lugs, crown guards identical, even period correct bracelet reference VD).

So what do the experts think?