The half penny was discontinued in December 1984. I wonder how long before that the eleven and a half pence stamp was purchased! Fancy still being able to put it on a letter.
The Ebay sender put a tiny address label in the bottom left of envelope and the stamps around it, very strange way to do it, so they couldn't be franked. Shame as the rugby ones are advertised for 99p on Ebay so the two would of been worth more than the envelopes contents.