lets be generous and say he only wanted a "souvenir"
suppose some small child had come across it or he had been burgled - it wouldn't be too good
If we are ungenerous we have a man with an unlicenced firearm in the UK who think he might need it some day....... to kill someone
I suspect the court got it just about right - he was damned lucky he didn't finish up with the Met Fire Arms squad breaking down his door at 06:00 and shooting him