Hi Mick, good fun. It's a bit hard to tell from the photo, specially with the bridge missing, but if the scale length (nut to bridge, once you put a bridge on) is about 14", its a standard mandolin. If it's around 17.5" it's more a mandola and suitable for C-G-D-A (I would just use medium gauge mandolin strings, rather than branded mandola strings, which might be a bit heavy for such an antique.)

I think with the guitar body it will have a nice mellow sustainy sound, like the Martin mandolins do. Defininitely not a bluegrass chop.

Bill