How did this post get a ‘dumb’ ?I honestly don't see the problem with removing the piccie. That brittle backing paper will have to go anyway, but the rest is really a five-minute (or less) job. The only possible difficulty could be the sprigs holding in the glass, mount and piccie. They might be rusty and need a bit of gentle persuasion. The frame itself is also brittle at the mitres (see the top right mitre in your piccie) due to the hoof-glue used at the time. All in all, demounting, cleaning, repairing and properly reframing is a 30-minute job. If you need any instruction, let me know.
Let’s all try to help get this sorted
Mentioning things like brittle backing paper is a helpful thing