These sturdy little plastic egg cups look very much like little space rockets, especially if you've got a very pointy egg.
They were made in the late 40s, early 50s (when the BEX stamp that is on the bottom of these was used) by the British Xylonite Factory which opened in the 1930s and for whom Mrs Thatcher worked as a research chemist between 1947 and 1951. 
These are way too much fun for the Not at All Frivolous Mrs T to have had anything to do with and provide a Pleasingly Futuristic and Solidly Functional Aid to Boiled Egg Enjoyment.
No vintage breakfast table is complete without them.
I have them in either pink or blue.