What is the penalty for 26 US Court 5861 d possession of firearm?

Answer 1

I believe that you may be quoting the Docket number or some other reference number pertaining to the actual case.

The exact charge and statute number would have to be known and insufficient information is disclosed with which to give an answer.

If it is in reference to a "Felon in Possession" charge - - look up the applicable US Code (which in this case would be 18 USC Section 921 & 922). The penalties would be spelled out there, which could include imprisonment up to 15 years in federal prison.