It appears there are a number of rifles in circulation with such apparent irregularities. I've handled one .243 Featherweight with a serial number that seems to indicate it was produced a couple of years before .243 Win ctg was commercially introduced. No evidence I can see that it was rebarrelled.
It is my thought that Winchester produced a buncha actions, serially numbered them that simply went into parts bins or onto the racks, to be taken out and barrelled as needed. If the older ones got pushed to the back as newer ones were produced, there's no reason you mightn't see an action with a 1952 serial number which wasn't actually assembled and shipped until sometime in the sixties.
No insider information; pure conjecture. It's my theory and I'm sticking to it.
Best,
Johnny