I presume you are classified in the Class "D" section. So for the first 700k, its tax at 15%. From what I read, you need to find out the value of the M6 at the time of his death. You will be paying 15% of the value. This must be paid within 8 months after death. I'm not a lawyer, but I guess you'll wait for the answer.
'16 F30 340 XDrive - AW-Lighting & Track Packages. The FIRST drive was awesome....