I dug out an 1895 Marlin in 40-82 and also found some Jamison brass. How good is the brass? 
And yes I know it’s not a single shot but matches I go to allow levers loaded one round at a time.

Same experience here Jamison is good brass.  Their range of offerings made shooting old guns much easier. It was a sad day when they were ended by ATF.  
As I understand it they were found guilty of violation the Obama ITAR license law .  After that we quit exporting even to Canada. The annual fee for the ITAR license is just too high.
We still have a few Canadian shooters that drive down to buy our NASA BP bullet lube .  I asked one why and he answered " because I want the best "