The calculator is 190mm [7.5in] in diameter. Its three disks are made of metal, probably aluminium.One side can be used to calculate the effect on people, structures and military equipment of an air burst nuclear weapon. An air burst occurs when a nuclear weapon is exploded so far above the ground that its fireball does not touch the ground and therefore does not suck up dust into the fireball. An air burst produces much less fallout than a surface burst and would normally be employed against an unhardened target such as a city.
The other side of the estimator can be used to calculate the effect of a surface burst. These would be used against hardened targets. A surface burst produces fallout, some of which may drift into the attackers territory.
The acronym CDEE appears on both sides. I think this may refer to the Chemical Defence Experimental Establishment, which was based at Porton Down in the United Kingdom. CD 7715 may be the identification number of the device. I do not know what DNBCS means, though the NBC part may be Nuclear Biological Chemical.
The Estimator may have been intended for use by military officers or civil defence units. It may also have been created to be used in modelling different scenarios in war games.
For more posts about Cold War calculators click on the Cold War Calculators category on the right.