Analysing the Leutwitz Apollo (6): Dr Northover's First Samples

A long time ago Peter Northover gave some of the lectures on metal analysis in one of the courses (conservation and materials science) I did at University, so I am interested in what he had to say about this object's corrosion. He seems not to have seen the object. He had received three samples and sent a report (not published by CMA) on November 10th 2003. The samples are simply referred to (p. 56) as:
1) the left hand and forearm
2) the right upper arm
3) the base.
The spectrometric results were rendered difficult by the corrosion, the characteristics of the corrosion . of the two samples from the statue suggested "a very long period of time exposed to a burial environment".

The third sample form the base appeared to be different, something confirmed by the different corrosion history [...] the base has corroded differently, although naturally. It has certainly been added later to the sculpture, not recently, but no earlier than the Renaissance.

This was earlier reported to public opinion by Stephen Litt ("A god of myth...") in the following terms:

Peter Northover, a materials expert at Oxford University, said his analysis shows that the alloy in two samples taken from the sculpture is similar to those in other sculptures from ancient Greece and Rome. A third sample shows the sculpture's base was made between roughly 1400 and 1900.

In the absence of Northover's actual report, it is interesting to speculate how we get from the one to the other. Again, any assessment of what conclusions we can draw from this are hindered by a total lack of detailed information where the  samples were taken (particularly important in the case of the base). In the case of the two arms, the obvious place to saw a little bit out to embed would be from the broken surfaces, suggesting that the breaks which have corrosion on them showing "a very long period of time exposed to a burial environment" were not made by the Red Army in 1945.

No characterisation of the corrosion products is given by Bennett in his reporting of what Dr Northover found, so it is difficult to know what it was about it that declared the patina on the part of the base analysed a natural patina. Neither is it clear why Northover says it was "not added to the sculpture recently" (was he informed that the base is apparently not in fact joined to the sculpture?) Did his  assessment come from the spectroscopy of the sample, or some other information we are not aware of? Also what makes its attachment necessarily post-Renaissance? Again, is there something in the analyses we are not told by Bennett?