Hi Ropat
Briggs did provide a conversion kit to Ford in US & Canada which would have been at least the door & instructions for fitting etc. I have seen photos of rear door Tudors up to the 1936 flatback Tudor. First ones appear in 1928 before the release of the Deluxe Delivery. Also it is not to say that other conversions were done by body shops making up a door ie. not from a supplied kit.After all these years of commercial abuse, it would be hard to know the exact origins of a Tudor delivery.
Here in New Zealand, they were known as the Commercial Tudor Delivery by the NZ agent for Ford Canada [ no Ford NZ until late '36]. They are very rare here, I know of only one restored & in mobile condition.I recall one or two in 1960's, all rough or only bodies of, usually with the rear door missing.
The body numbers here are 4F..... which shows they started as a Tudor. You may find a number on the steel member in front & below of passengers seat [ on floor] but I have heard that the Sth American cars do not have a body number even though manufactured in US. Being Tudors, the bodies were not made by Briggs, [they are a Ford built body] but the door kit was developed by Briggs. Regarding rarity, it is only my opinion; do you know of another in Argentina?? Actually, there are a few in US [ maybe 4 or 5,also a few fordor types known as 'flower cars''] which appears more than anywhere else. Most 'foreign'markets were small so cars new & ones still surviving will be minimal. The largest numbers of any Model A's are in US & Argentina & other Sth american territories. Hope this is of help.