Black ring on my bulbo's leaf
 

I got B Sikkimense a couple of weeks ago and has developed the dark ring which I assume is a fungal infection.

I encountered this previously on a Vandopsis leaf which eventually fell off despite me trying to cut out the area but didn't kill the plant.

For my better understanding on the cause and resolution would there be someone familiar with this, it seems specific to newly acquired plants so assume change in environment (cool), lack of air flow or sitting in a box is the cause. I'm hoping I can treat it before it spreads.

I think you have diagnosed it correctly. If it were my plant, I'd surgically remove the bad spot and some clean tissue around it (single edge single-use razor blade works really well, a nice clean cut), dust the cut with cinnamon.

I think you're right on all counts on possible causes. Especially, if it experienced cold during shipping it can take a bit of time for the damage to show up. Depending on where it was shipped from, and your weather (you're getting close to winter) perhaps in the future asking for a heat pack might help. I have found that newly-acquired plants, even though they might be theoretically cold-tolerant, need to be pampered the first year, since vendors tend to grow things in greenhouse for control, and so the plants arrive not acclimated to temperatures that they should be able to tolerate They eed to go through a full growing cycle to be ready for following year's chill.