My recollection is that before the recent changes, the first character was the fare bucket (not merely the booking class) which now seems to be 4th from the right.

I've got tickets going back several years where this appears to be the case.

If a fare bucket can belong to more than one booking class now, as mentioned in post #2 above, then I can see a requirement for two fields to contain what was held in one field before.

My question was, did that come about at the same time as the recent changes?

Is there a list of all the possible alternatives?