Stephane, I appreciate your quest to replicate that artwork as I have gone through similar dilemmas. I downloaded the picture that you posted and even at that resolution most of it could be reworked to satisfactory results. The coat of arms with the lions will be the tough part.
I have often gone to the site that an internet picture that was posted to and researched the photo or tracked down the owner of the item. If it was on a web site, I will join and contact the poster. If it was an auction, then track down the the seller or contact the auction service to see if they can put you in touch with the seller or buyer. Sometimes I got lucky, other times I found a sympathetic ear to my cause who put me in touch with a source. Of coarse, I struck out a few times too. It is surprising what can be tracked down with a keyboard.
Here is a link to another similar safe. It is at an angle and the resolution is worse than yours. I would contact the auction house in the UK and see if they can help. With the white background a good picture of it would work. The auction is from 2015, recent, in scheme of old safes.
https://www.invaluable.com/auction-lot/a-vintage-chubb-cast-iron-safe-the-door-applied-1224-c-d5c4cf48ad
Working in Photoshop or Illustrator, amazing things can be done with a crappy picture but it is time consuming and using a professional person is cost prohibitive.. If you don’t have the computer skills look for someone who is retired or a high school/collage kid who yearns to be a graphic artist. Some of the young people are a whiz at these programs. I placed a Craigslist ad for one and found an underemployed fellow who was pleased to help me in order to make a few extra dollars. Good luck, where there is a will there is a way.
