It is definitely expired old film! Duncan, you may have something there. I really doubt that the guy who sold it to me was really "cleaning out the film fridge" as he suggested, unless he forgot to mention that said fridge had not been plugged in for 8 years or something. I acquired other stocks from him and not all were good (but some were) - in fact some Reala 500D seems to have dropped to about 100D which is quite a toll. So it could be an effect of uneven heat here. Odd though that the edge seems more sensitive than the rest of the film, or at least seems a bit more dense, hence lighter on the scan.
I guess so far we have the following possibilities:
1. Light got to the edge. Probably debunked by the fact that the sprocket holes are clear. And I used the same loader to bulk load some Portra that seems fine.
2. Bad or insufficient chemistry - but I just used the same bleach and fix on some Portra with no apparent adverse effects, and the ECN-2 dev was freshly mixed from dry chemicals and previously unused.
3. Bad storage/uneven heat. this seems to be where I am going.
The negatives were very thin. Presumably, another aspect of poor storage would be speed loss. The question is: If I reduce the EI of the film and re-test, will the difference between edge and the rest of the negative be as pronounced with a thicker negative as it is with a thin one? Perhaps not, given the exposure latitude to over-exposure that most negative films possess. I will try to get to that tomorrow and see how things go. I am sure this was quite an awesome film stock once upon a time.