teeny weeny mystery copper coin now gone grey ?

[chantalpoole]

mystery teeny weeny coin got soaked and now its gone grey with brown splotches on it.i can see more pattern but its still hard to make out.i know the image is under the tarnish i can see it better when the coin is wet .
my question is what is it made of ??
is teeny weeny coin silver with brown corrosion ??
was old silver mixed with anything that would have made the surface greeny tinged (it never had corrosion just a greeny bloom in places?
iv never had a copper coin go grey before after a soak in bicarb

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[Chef Geoff]

It's probably still a Roman bronze, bronze is a mixture of copper and tin tin being grey and if you've soaked it in lemon juice then two things will happen ₁ you will burn in hell for that and ₂ the weak acid will attack the copper but not the tin as will sea water

[chantalpoole]

it had a bath in bicarb soda

 

as it was it may as well have been a pebble 

[Chef Geoff]

No not at all, it gives you an idea of what may be there especially after cliff falls, after a few tides the sea will have liquefied the mud and clay allowing any heavier items to be released so just keep checking the same areas and you might find some nice goodies