The stamp on your maple neck most likely indicates 1973 (or 1976), whatever makes sense with the rest of the bass (I'll explain in a bit..). Here's what the code means..
01 = P Bass
03 = fretted maple neck
19 = 19th week
The last 2 digits is where it gets confusing. Normally the 2nd to the last digit indicates the year and the last digit indicates the day of that week with this style of code (and there were actually 3 completely different neck stamp/codes simulateously being used by Fender in the early '70s). I've seen many examples from the early/mid '70s in which the last 2 digits are switched with this particular style of neck code (so the 2nd to last digit would now indicate the weekday and the last digit indicates the year). This is coming from someone who has seen hundreds of these codes over the years (me). I personally believe the inconsistency was due to some employees simply marking them one way (the newer way), and others employees marking them the other way (the older "batch" code way of the late '60s). They were both sort of confusing code systems, and all the while, Fender was still often using the regular 'ol date stamps at this time too! Then add in the fact that no one making these necks back then probably ever thought any of this would even matter beyond the factory anyways.. and voila, you get some inconsistencies.
So with these old Fenders, you always have to look at them as the sum of all their parts, and play a little detective sometimes to get an accurate date of manufacture. You said your ser. # is from circa 1972 (and there is ALWAYS an overlap of about a year or so with all Fender ser. #s because the neck plates were ordered in bulk and were used on all models of basses and guitars simultaneously and grabbed randomly from boxes). To date your bass, you will also need to get the codes off the pots and the codes off the undersides of the pickups to have any real accuracy. If everything dates to around 1973, then your neck stamp would most likely indicate - week 19 of 1973, day 6. If the paint transfer between the neck and body matches and the rest of the bass has the correct appointments for that era, then it's safe to call it a 1973 at that point (or whatever the last date-able part you can find is).
Now, it's possible that the neck could be from 1976, but that's why you look for any signs of that neck being mismatched to that body, as well as the rest of the appointments on the bass... Beginning in 1976, Fender started making changes to the tuners they used, the way they routed the bodies, the headstock decals, etc.. So if everything else on the bass is mid '70s style, then the neck code would indicate 1976. And likewise, if all the other parts and appointments are early '70s style, then the neck code would indicate 1973 (assuming that it's not a parts bass that was thrown together by someone before you).
This is one of those small tidbits of info that very few people know about unless they have worked on or owned a huge sample of Fenders from this era. In other words, you aren't gonna find this info in any books, but I assure you, I've seen this many times. Hope I didn't make it more confusing, lol. If you feel like taking the bass all the way apart and posting the pics, we can figure this out definitively.
