ECR is Eric Rohrbaugh.
There is no real correlation between serial numbers and the order guns go out of the factory. The serial numbers are produced sequentially when the frames are made, however--there are no guarantees after that. Frames out at at different times for annodizing, etc. and are assembled at different times. Sometimes whole runs of frames are refinished for one reason or another, which can be a significant delay for that batch.
I don't believe Rohrbaugh would sell you a "reconditioned" frame without telling you. I am not even sure that they do such a thing, or that it would be legal.