HMV Sound Box with plain backplate

[phyi9530]

Hi all, I came across this HMV sound box with plain backplate online. From the diaphragm, I think it should be a HMV 5B. There is however no marking at the backplate. I also noted that one of the screws at the front cover is missing. May I know if this would possibly mean that the backplate was changed at some point in time? Is such replacement backplate common and whether there is any known downside to it like whether its performance may be affected?

Thank you.

[Inigo]

It can be an Indian copy. They aren't of the same quality... prone to brittle fracture.

[Steve]

It can be an Indian copy. They aren't of the same quality... prone to brittle fracture.

That's exactly what it is, down to the "prone to brittle fracture" part, which is just what the British originals are!

[Viva-Toenail]

Perhaps a late Columbia 28a where the text was painted rather than etched and subsequently worn off?