Steve,
Only very roughly. The original engine number is best, because there's only one sequence of them. All the other numbers start from 1 (or 1001) at each factory. Your car is the 12,961st FE Special (225) manufactured in Adelaide (A). The first digit of the chassis number will tell you the year it was assembled (and the letter on the end tells you where).
This is all discussed at length in the
Tech Info section.
But taking a stab, I'd say November 1956. My car's ID is FE-225-5678, and it was manufactured in the first week of September. (It was also made in Adelaide - all the early ones were manufactured there, hence no need for a distinguishing letter).
I'd be interested for my own research if you could tell me:
1. What the chassis number is (it should look like 6-nnnnn-X)
2. Whether it has a thick, FC like rear window stainless trim that covers the rubber, or a thin one that fits into the rubber
3. Whether it has the supports between the wheel arches and the underside of the rear parcel tray
Actually, if you've got the engine number that would be good too. Check out the ID Plate decoder on the page I linked to above. You'll get a heap of info from it.
cheers
RET