Everything that leaves the transducer factory gets sold to someone - the same with the completed units --- How much do you want to pay? Do you want .1%, 1% 5% or 10% sir? -- you can guess the restVisually they all look the same to me. I have 3 such units, all from different eBay suppliers and they all 'look' identical.... I believe this is to do with the Transducers, which although driven by what appears on my scope to be the same signal, they do vary in timing and response.