Info on old bottle needed please

Hello,

I'm not really a bottle collector myself but my fiancée has quite a few
bottles that she has brought up from the Solent on various diving trips.

One bottle we have would appear to be an old black glass shaft and globe
bottle. It is less than perfect (as to be expected from being under the sea)
and appears to covered in something. I am unsure what this stuff covering it
actually is. My first thoughts were that perhaps it was sea bed sediments
that had formed concretions around the bottle but now this is flaking off
the bottle and exposing the glass underneath. The flakes are brittle and
shiny black in appearance, a  bit like old tar.

My question's are:

What is this stuff on the bottle and should it be flaking off?
Is there a way to safely remove it without damaging the glass?

Here are links to some pictures, apologies for the file sizes (400-450kb
each) but I wanted to get some detail in the pictures.

http://members.lycos.co.uk/cabriolet214/FrontDownward_view.JPG
http://members.lycos.co.uk/cabriolet214/RearDownward_view.JPG
http://members.lycos.co.uk/cabriolet214/Rear_view.JPG
http://members.lycos.co.uk/cabriolet214/Pontil_view.JPG
http://members.lycos.co.uk/cabriolet214/Crest_view.JPG

Thanks in advance for any info you can give.

-- 
Michael Cotton







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