In the last few days I have followed up Sue's comments - the entries for Andreas, Michael and in part St Marks look as though complete years or decades were re-transcribed and entered into the IGI under various batch numbers in the 722xxxx and 723xxxx series which appear as Patron submitted records prior to 1991 (call these the 'new' entries). When you fit these up against the remaining entries claiming to be from Parish Register transcriptions (call these the 'old' entries) it is obvious that those old entries which matched the new entry were deleted and thus appear with the 723xxxx batch, those that did not match (eg changes in transcription) remained thus giving the highly useful result that most of those that claim to be parish records are wrong transcriptions whereas the possibly more accurate ones are tagged as the generally unreliable (and at times totally spurious) patron submitted variety.
The new entries for St Mark's were entered as 'births' but the few overlapping entries (ie mistranscriptions) show that the birth date was the christening date. Both these observations need checking with the Museum films but the new numbers agree with what I expected from simple demographics and show no other obvious bias (eg towards dates or families).
The 1911 transcripts were from the films I saw in the Museum in a clear hand but for example in Arbory it is obvious when all names are put into an easily accessible database that 'u's and 'n's were wrongly read in that a large number of Clagnes and Tanbmans apparently settled in that parish.
Has anyone any idea what was going on here ?