I have some of these and they are most definitely a rebranded Lexmark Keyboard. I think at one point I saw a lexmark keyboard with the same part number on ebay and the "LX" that it starts that model number with is kind of a hint at that as well. There is a sticker over the main IC, but if you remove it, it says Lexmark on it. Picture attached. Seems to have something different about the output though, only about 1 in 20 key presses registers with Soarer's converter. Pull up resistors didn't help, so not sure what to try next.