The original, authentic Lignum Vitae is now on the CITES list so is no longer imported. Here are some pieces I've had kicking around the workshop for donkey's years,
Even though the colour varies dramatically from board to board it's still fairly easy to identify, when freshly cut there's usually a greenish band somewhere, fresh cut it smells extremely sweet, and it has a waxy or oily feel to the surface. Add in the extreme weight and hardness and I've never seen anything else quite like it. Give it enough time and it generally blackens.
It's probably the most difficult timber species to work that I've ever encountered. You can't easily glue it or screw it, it knackers tool edges after just a few passes, the grain is interlocked and prone to tear out, I use an M42 bandsaw blade to cut it and even then you have to proceed at a snail's pace because it clogs up the gullets with waxy sawdust that sticks to the tool. I've never turned Lignum but I suspect turning is really the only practical way of dealing with it.
From a furniture maker's perspective it's pretty much useless, for all the applications that you'd think Lignum is ideal for (drawer runners, tool fences, etc) I find some other timbers like Rosewood or Ziricote give almost the same benefits but are just far easier to work. Interestingly it does crop up fairly often in antiques from the 1500's and 1600's, especially in kitchen ware. I don't know for a fact but I suspect it's because Lignum's medicinal properties gave it a certain cachet. Up until the 1700's Lignum Vitae was listed in the excise and customs registers not as a timber but as a medicine, I believe it was used as a treatment for sexually transmitted diseases. Maybe that's why you see elaborate communal drinking cups from the Tudor era made from Lignum?
Anyhow, to the OP's question, I don't know what your board is. It's not original Lignum and I'm pretty sure it's not Iroko. Where did you get it from? Sometimes the source is a more reliable clue than the photo.