Here are some things that you don't see every day--two stamps with overprints in what appears to be the same font and using the same kerning (that is, the same amount of space between letters) on stamps issued decades apart. It is a bit difficult to tell this because the Specimen overprint is indistinct on the left side.
Even more intriguing is that the House of Commons overprint has never before been reported.
The final overprint--complete with
misspelling of "Northern" as "Northen"--is on a stamp not previously
known to have been overprinted and the company overprint has also not previously
been reported. Also, I have been unable to find any reference to the Northern Gas Company ever having existed outside of the Middle East--and even those references are recent.