To ask if you can identify this hallmark?

[DickDastardly]

It's hard to read but I can see the crown and 750. Maybe a Q?

Sorry! I've posted this in 2 different places. Oops.

Is the one on the far left the leopards head, London, hallmark?

Try this hallmark wizard:
www.gold-traders.co.uk/hallmarks/

There are other lists you can google for with the date letters which might help too:
www.bullionbypost.co.uk/index/gold-and-silver/hallmark-date-letters/

750 18 carat gold.

Crown = gold

Leopards head = lion

Date mark Q maybe? for 1990

That's my best guess from the photos. I'm better at antique silver than gold so I might be wrong.

Lion should say London

Could you try to clean it? Try soaking it in some gin, then use a toothbrush on it.