Your sheet is a snapshot of an entry
A birth, marriage or death is written into a register once and then kept there. A certified copy is a printout of that entry made on a particular day, sealed to show it is a true reproduction. The register goes on holding the entry after you walk away, and it is the register, not your copy, that offices treat as the real thing.
This is why what you need for an apostille for Germany is a recent certified copy rather than a treasured old one. The freshness matters not because anybody counts the months, but because a copy printed today shows the entry as it stands today, which is what a reader abroad is trying to see.
Two things with different lifespans
The certificate added in Milton Keynes vouches for one signature on one page. Its subject is that page, not your circumstances, so it neither expires nor updates. An apostille issued in Coventry for use in Germany is fixed to the sheet it arrived on, and lifting it onto a newer printout is not something any office does.
The entry underneath has the opposite character. It can be corrected, added to or superseded, quietly and without anyone telling you. So the two halves of what you are holding age in completely different ways: the certificate stays exactly as true as it was, while the paper it sits on can slowly stop describing the present.
What Germany needs from the pair
Germany joined the Hague Convention in 1966, so an apostille for Germany is the correct and sufficient certificate and no consulate takes any part. Document legalisation for Germany therefore stops at one desk, which makes the route short and the timing easy to plan. One office, one fee, one certificate on the sheet.
That simplicity puts the whole burden on choosing the right sheet. Nothing later in the chain compensates for a copy printed before a change, and no reader abroad can tell from the certificate alone how old the printing is. An apostille from United Kingdom to Germany certifies the page in front of it, faithfully, whatever that page happens to say.
Ordering at the right moment
The practical rule follows from all of this: order the certified copy when the need is real, not months in advance to feel prepared. Coventry Register Office, Cheylesmore Manor House, Manor House Drive, Coventry CV1 2ND, holds the civil entries registered in the city and can print one whenever it is asked.
Where a paper comes from a court, a college or a company, the same logic applies to whichever body signed it, and its own rules decide how many signed sheets you can have. Allow for two waits in your timetable — the printing and the postal turnaround — and remember that each varies with how busy the office in question happens to be.