ACCo and funny m year mark

by Jay
(London)

Hello,

I have a ladies wedding ring which I am trying to find some information on.

So far I have managed to determine it's English, 22 carat and has the Chester hallmark on it; however, the year mark especially seems to have beaten me.

As can be seen in the images, it is a left slanted 'm' with a tail coming off and under it. It doesn't seem to match any hallmark sheet I have seen.

As a side I would also be interested in what company made this foes anyone know:-)

Thanks in adavance!