Determining colors on computer monitors is a study in inaccuracy due to all of the variables involved.
Below is a purported (meaning no certificate) 1294b, black violet from a reliable source.
This does seem darker than your stamp in question. Edit: now that I could look at the images in the thread together, the image here is clearly much more dark and lacking the amount of violet tone in your example. I can say, yours is not the black violet.
Additionally used stamp that have been soaked have their own issues about maintaining original color.