Internal manhole. How to lift cover?

[Mattg4321]

As per the title. Any ideas? Is the round thing some sort of cover over the slot where a key would be inserted? 
 

Dates from mid 80’s and flooring is old Amtico. Can see the outline of the manhole where the flooring has been cut round it (very well actually!). There is another round cover thing at the other end in the middle. 
 

[Mattg4321]