Friday 9 October 2015

"The corrosion on the coin makes us believe it likely the coin was a recent find".

Screen shot showing atypical corrosion
which PAS says "makes them believe"
 Message from the PAS about the discovery of that Komnenid coin:  (SF-3175A4):
Sorry for the delay in replying. We are reviewing the use of the ‘comments’ box as there is some overlap in how people use this and ‘error reports’. On the issue of the find in question, we have no reason to believe the find was not found where the finder’s says it was discovered. But if you do have evidence to the contrary do let us know. The corrosion on the coin makes us believe it likely the coin was a recent find.  Best wishes, Michael
"No reason to believe" is what no-questions-asked dealers and collectors say about the origins of masses of undocumented artefacts on the market. This is, as we know, a huge cop-out to circumvent the process (due diligence) of enquiring properly into the origins of an object to identify illicit irtems 'laundered' through precisely "no reason to believe". But verifying the information supplied by the profferer is what both collectors (and here archaeologists) should be doing.  After all the whole point of the PAS is about emphasising the importance of findspot and inculcating that message among collectors, here there seems to have been an elementary failure to do the footwork themselves. A mere "no reason to believe" is not a provenance that one can believe in.

Many years ago, I wrote my undergraduate thesis on metal corrosion products and their relation to burial environment taphonomy. Most of us archaeologists believe that form and chemistry of the corrosion on buried metal objects is an indicator of the burial environment (as I wrote)  rather than the time that elapsed since an object was dug up. Mike Lewis writes here almost as if the PAS believes that corrosion self-destructs at a certain rate and that if an object from the ground has no corrosion on it, it must have "surfaced" a long time ago. This is patently false.

To be clear, I am talking about a plate of black crusty corrosion coating a silver object and not removed by any cleaning treatment. I would think this is a sulphide rather than oxide, but there is no mention, let alone description, of this unusual feature in the PAS 'record' of this object. The PAS seem to think such corrosion is common on the crag sands  of Suffolk. I'd like to see them prove that by showing us other ancient silver objects with the same corrosion on them - handed-in-for-recording hammies for example.

Screen shot showing craters which PAS says "makes them believe"
Just "what" about that corrosion is it that "makes" the PAS "believe it likely the coin was a recent find"? The redeposited metal maybe? The etching that apparently goes under the crusty corrosion? The odd circular craters in its surface (click to enlarge)? The localised and amorphous form of this patch of corrosion? Please, PAS with all your experience in handling ground-dug silver coins from similar soils to that of mid-Suffolk, show us some more examples of these features. 

I think this is another case of the PAS not reading an argument before dismissing it and not knowing what they are talking about. My tracking software shows that Bloomsbury did not access that post before Mr Lewis replied. What guarantee is there of the integrity and reliability of the 'data' the organization collates if the collection of information is carried out so uncritically and without double-checking?

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