I have been the owner of a Temlette Seven String banjo for than thirty years ! I bought it in dubious condition and had a new vellum put on at the old Clifford Essex shop in London . The old guy who ran the shop told me it would have been tuned however you tuned your Five String , with a low C and G for bass runs for song accompaniment .
I still drag it out for a plunk every now and then - a real Fun Machine !!