The marriage record was in Hebrew. Ha-Kohn (הכהן) is the Jewish title meaning "the priest", it was not a surname, but Samuel clearly adopted the anglicised form Cohen.
The United Synagogue Burial Office has informed me that there are no surviving burial registers for the West Ham cemetery. That's a bit of a blow. I have one other contact at the US who has taken photos of gravestones for me in the past. I'll ask him if he'll be visiting the cemetery anytime soon.
Or do you happen to live nearby?
If you have an ancestry subscription, you could contact the owner of the family tree which shows that Moses was the son of Asher (see
http://www.rootschat.com/links/01qiq/) and ask about the source.
It's strange that Elizabeth's father was recorded as Joseph on her second marriage certificate. For the marriages of her siblings (Isaac Michael (1841), Eve (1861)and Catherine (1848)), the father was consistently recorded as Moses. Moreover, when Elizabeth was finally baptised as an adult on 4th Apr 1869, she said her parents were Moses and Sarah (see
http://www.rootschat.com/links/01qir/).
I would speculate that the entry on the 1866 cert is a simple mistake that Elizabeth was unaware of as she was presumably illiterate, i.e. she couldn't sign her name.
Moses died on 22 Dec 186
3 and was buried in the West Ham cemetery on the 24th.
Justin