It'd be a bit tricky if you do not know how what levels you spent in what classes.

If any of your characters auto-joined at high level or otherwise leveled up all in one job class, then, yes, you can use trial and error putting raw stat numbers into a spreadsheet until you find the minimum and maximum raw stats that character could have at his level, and then use those raw stat values to see what range of stats they would have allowed at lvl 1.

The spreadsheet I've been using for years seems to have been lost to the processes of internet geology, so I will make a public google doc for us.

https://docs.google.com/spreadsheet/ccc?key=0AviQt93JXScudEZVU1ZqN2NXZm1pYW5mVVVkaHJ3SlE

So, example: your 99 Balthier has 332 hp naked. As he is male, he has male hp growth and his raw value at lv 1 had to have been between 491520 and 524287. Let's narrow that down.

On the Stats by Lvl sheet, I put 10 and 110 in for C and M respectively (as those are the correct figures for Baltheir's job, as per the second spreadsheet). Feeling hopeful, I put in the max, 524287 under RAW VALUE. I look at the bottom (or make a cell near the top reference the proper cell, to save scrolling).

Putting the max returns 348 hp at lv 99, which is too high. Ok, let's try the minimum, then: 326; too low.

Let's try something in between, then. 500000 returns 332. Great. Let's see what is the lowest value is that still returns 332.

495000 is too low, so we go higher. 499000 is very close. 499500 works. 499300, yes. 499150, yes. 499050, yes. 499020, no. 499030, no. 499040, yes.

So now we know that the lowest raw hp value our boy could have had is between 499030 and 499040. x35 is too low. x38 works. x36 is too low, so we know that the minimum value we are looking for is 499037.

To get the maximum, do the same thing going upwards from 500000.

You see, it's quite simple. But it's only this simple if you can use the calculator, which presently only does a straight stint in one class.

You can narrow down this value even further by checking at each level as you level up, but once you have the 99 figures you can put them in and look at what lv 1 returns to see the minimum and maximum you could have had.