This is a 20 year old atag.
They use the same condensing main heat exchanger on todays boiler.
Only boiler company to offer a life time warranty on their main heat exchangers.
Only reason boiler got removed was because of the flue.
Vokera unica HE main heat exchanger has corroded through time for a repair. New main heat exchanger required.
These are its pipes
Here is a vokera boiler that I squeeeeezed into a kitchen cuboard.
This is called a low loss header that I have installed under the boiler, it allows me to fit a bigger pump as some of the far radiator were not getting hot.