Nice gun Mark,
This is an early back action lock. The bar part is not needed and allows more metal to stay on the action. The best H&H doublerifles are built that way.
This gun has the Webley look...Any number on the barrels forend loop or in the vicinity? (I would guess 8xxx or 9xxx)
I would say 1890s vintage...
The urn on the bottom of the action was fairly common on Manton guns. I don't know what it means, or what is the story behind it.
Best of luck with it!
WC-