Hi James, welcome to the GMB.
Try dusting the signature area with talc and wiping off lightly. That should make the signature easier to view.
Also, if you can, get in as close as possible (while using the camera macro function) to fill as much of the image as possible with the signature. If you cannot get very close, then use a plain white background and that will stop the camera focusing on the background rather than the signature.
And a side-view photo of the whole thing may help to get an ID as sometimes just a shape and decor will suggest a maker.