Which is the most dangerous. Small metal item is an unexploded fuse which is unstable and has the potential to remove a number of fingers or a hand. The unexploded shell happened to be armour piercing which is just a lump of metal. The high explosive version is almost identical and after 70 years will be unstable and lethal to anyone disturbing it and those within 100 metres.
The 75mm shell shown is a S.A.P.(Semi Armour Piercing) which had a Tracer content in the base, the 75mm H.E. is NOT identical to the 75mm S.A.P; being 11.5 inches long (including the brass nose fuse) the S.A.P. shell being 8 inches long. The “small metal item” appears to be a 37mm HE and the fuse looks like a No. 119 A.A. shell fuse. The 75mm HE shell found on Upper Midhope range are of French WW1 vintage, brought over to U.K. in 1940 and taken from French Dumps before being over run by the invading German Army, because this ammunition was “old stock” it was only allowed to be fired on practice ranges.