The brand seems to be MEREX or something like that.
I'm attaching a picture.
I can't find information about it.
Does any of you have heard about this brand, any web page, some technical papers?
I need to know something about it's internal parts, and how it works without disassembling it.

It looks like a 3-way nonlubricated plug valve.  
There's a tapered plug loaded into a (probably teflon) sleeved body.  The triangular gland flange on top loads the plug into the taper so it will seal.  

The plug has a cutout that bridged the common port and one of the side ports.  Rotating the plug 90 degrees closes one outlet port and opens the other.  

THe body has an ASA rating, which is an indication of being at least 40 years old.  ASA was replaced by ANSI which is now ASME.  

Similar to a Durco Sleeveline 3-way. 

Nordstrom refers to the stuff as "Sealant" and there are many formulations based upon compatibility with the process fluid.  

You can use that same Flowserve link I gave you previously, just put in "Nordstrom" for the heritage name instead of Durco.

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