Milner safe information

[Markfd]

Hi everyone,
I am new to this forum & am looking for information about a Milner safe that I inherited off my father. He acquired it in 1963 in a post office that he ran. I can’t see any serial number on the safe but there is one on the original key. It says Hobbs & Co patent, 76 Cheapside . 56108
The plaque isn’t original, I bought it on EBay & the fixing holes were not in the correct place.
After studying your website, I think that it dates from around 1852, is this correct? Does anyone know what the rating would be for jewellery insurance purposes? I presume that it is a 212 document safe although the walls appear to be 1/2” thick. Also, is the handle original, I have seen a picture with a similar one, but most seem to have a lever.
Any information would be useful.