Short answer: Correct. The Shipping Order (SO) number on a 67 tag is NOT sequential. The SO is related to the SPD meaning you can't compare the SO between cars and learn much. It's likely the first "3" in the SO indicates the car was built for a reason outside of normal retail production i.e. dealer demo, lease car, etc. Don't ask. I don't know what the 3 actually means but it means something.
Long answer: SO assignment in 67 is different than later years. The first two numbers of the SO are related to the series and price line of the make and model in question. The first two numbers go up as the price goes up.
For example (and based only on my understanding today, the info I have on hand, other examples may exist, this may change in the future, blah, blah, blah, research continues.....)
Valiants start with 00 (possibly 01 also but I don't have an example of that)
Barracudas 02 or 03
Belvederes 02 or 05
Darts 03, 04 or 06
Coronets 06 and 08
Chargers 08
Full size Plymouths 08 or 09
Full size Dodges 10 or 11
Chryslers 12 or 13
Imperials 14
If a car has a different first number than would normally be found in the series, then it's safe to assume the entire SO series has been reset. The car has been assigned a specialty SO for some reason (again, it was a lease, dealer demo, show car, 67 Super Stock, executive order, or a variety of other possibilities)
From what I can tell, the five digit SO number was reset each day making the Scheduled Production Date important. So the range of SO of Imperials built on 823 SPD would range from 14001 to at least 14647 or 647 Imperials built on that single day. The next SPD, say 824, the series would start over making the SO number for the first car built 824 14001. IF this thinking is true, then one should expect to find two cars with the same last five digits but with different SPDs.
The down side to this is you could no assign anymore than 999 cars to be built on any SPD without changing the first two digits. This is probably why the higher volume cars (Belvederes, Darts) have more than one initial series number. Given the total production of Imperials, it's unlikely they built more than 999 cars in one day. That's probably why there is only one series (14) number. As production ramped up during the 60's, this format would become unworkable. That reason, and probably a coupe of others, is why the SO assignment changes for the 1968 model year to a six digit number.
Being able to draw correct conclusions on topics like this is WHY information from tags, broadcast sheets, window stickers and other factory documentation is so important. Each bit of information tells us more as to how things were done. Each year is different. Each plant is different. Save the data.
! now let’s see if I can retain that info this time. It really is interesting.
