I am a new member here. I am respectfully asking for help confirming what I think I have learned from the 925-1000 Online Encyclopaedia of Hallmarks. I have the bellow Justin Vulliamy Pocket Watch (a family heirloom).

On the inside of the case it bears hallmarks which I have interpreted as the following:
Standard Mark: .925 Sterling, City Mark: London and Date Mark: 1786.
I am most unsure about the Date Mark as on in the Encyclopaedia the L series for 1786 does not have a rounded base to the shield as shown on mine. Is there something I am missing about this mark?
Are these interpetations correct (please remmber I'm new at this)?

The same Hallmarks appear on the inside of the case behind the movement:

Any help you can offer pointing me in the right direction would be appreciated. Also I can not find the Maker's Mark in the Encyclopaedia. If anyone recognises this "HG" mark please let me know.
Regards,
Zac