Well...if it was found with a John Grey set, I'd say its also most likely a John Grey snare drum....
It wasn't a full John Grey & Sons set, just the kick drum. I did consider this however but the hardware on the snare doesn't seem to resemble anything i have seen in the photos of John Grey drums which I have viewed on the net or seen in any of their old catalogs that I have managed to download.
In addition to this, the outline of the badge doesn't seem to match the shape of those I have seen on John Grey drums.