Gas tank safety certificate

We have not used the gas central heating system as we use a large wood burner for heating since we bought the farm 8 years ago, the gas tank is a large above ground tank originally installed by Finagaz.
We have had the central heating system serviced and upgraded and have taken a contract out with Antargaz who we believe filled the tank for the previous owners (who we can’t ask about it as they are dead) and they are saying we need a DPE safety certificate for the tank that they own according to them, we intend the gas heating as a winter backup only.
The tank was installed in 1971 and was only used in the last 10 years for the gas hob, we don’t have anything paperwork wise for the tank bar the installation receipt.
Does anyone know how we get an update new safety certificate for the tank and likely cost.

Would a local plumber be able to put you onthe right road, worth asking I would have thought even if they don’t do gas.

It is my experience when you buy a property with a gas tank the notaire tells you if you now own it and you have paid for it…or your gas supplier owns it and you pay rent, who has all the details and organizes the certificate , inspection and maintenance of paintwork etc You have to have the tank tested and examiner by law.
Thats how its worked for me… Never had a problem in 26 years but never changed gas supplier. I would start with gas suppler and ask for proof they own it and a estimate.
Good luck.