There is a lot of info, testimonial, advice, etc on this site for these. They were made by Aristo for rebranding by Zone VI Workshops (of Fred Picker fame). There were heads made for graded paper, and those for filter driven variable contrast paper. Your best option is to search for various phrases on this forum, you will find much to read.
I don't know where the firelands are, but if you are within phone access from Virginia, I can tell you a lot, if you want to DM me.
If it is a filter head, allowing the use of variable contrast filters, it opens up the technique of multigrade printing (various contrast grades used on the same print) - another search crtieria.