Out of curiosity...

[RSStone]

Had a couple of these in a recent bulk purchase, put one on a little portable job I worked on, amazing sound quality and very lightweight. I've looked online and seen the same model and style, except they had a nicer faceplate... What all information can anyone give me about them? Rarity and Value if any? Don't want to undercut myself any more than I want to overcharge someone, and it would be nice to have some basic info to pass along when I sell them. Thanks in advance.