097 is a heavy duty Sierra and standard Transit Diesel battery. 095 is a larger capacity battery still, even though the number is lower.

085 batteries are normally around 44AH and approx 390A cold-crank.
097 batteries are normally around 63AH and approx 525A cold-crank.
095 batteries are normally around 75AH and approx 680A cold-crank.

085 is a standard battery used on Escorts, Fiestas and most Sierra models.
097 is used on Escort and Fiesta diesels, Sierra and Transit diesels.
095 is used on Scorpio diesel, optional heavy duty for Sierra 2.5TD.

Obviously there are more models that use each various battery, the list above is just examples.

Best to remember as well that there is no point using a 45/55A alternator to run a car with an 095 battery with lots of electrics running, the same as it is not worth having a 95A alternator to run an 085 battery.