Proving a British signature abroad
A foreign office has no way to recognise a British signature by sight, so it relies on someone it already trusts. Treaty members trust each other's single slip. Everyone else asks their own consular officer to look at the file first. Turkmenistan belongs to the second group, which gives this job two distinct stages.
Turkmenistan and the Hague Convention
Turkmenistan has not joined the Hague Apostille Convention. A British paper heading to Ashgabat, Türkmenabat or Mary requires embassy legalisation on top of the British stamp. The United Kingdom is inside the treaty, which is why an apostille is issued here without difficulty, though that has no bearing on a destination outside it.
The Sheffield end of the job
The British stage is postal and central, so no counter in Sheffield handles it. The city's contribution is the source paper: the Register Office at the Town Hall for civil entries, a university for a degree, a professional institution for a chartered membership, and a solicitor for a company document no register holds.
An apostille from United Kingdom to Turkmenistan is normally tied to a start date on a technical contract. That makes batching worthwhile. Send every paper in one round, keep spare certified copies at home, and treat the consular stage as the part of the timetable you control least.
Language, and the energy sector behind the file
Turkmen is the state language, and Russian remains in common office use, so the version you send should follow whichever the receiving office works in. Prepare that text after the stamps are applied. A translation made earlier describes the plain sheet rather than the marked bundle the file has become by the time it arrives.
Gas and engineering projects give the corridor its shape. Technical postings ask for a degree, a chartered membership, safety certificates and a police record, each proved before a permit is issued. Company records travel where a firm signs a contract or opens a representative office. Personal records move rarely, and usually behind a family move.