Differences between model number?

I’m looking to replace a broken mp3 player with the SanDisk Sansa Clip, but I noticed while searching online that there seems to be two different model numbers for what apears to be the same unit - SDMX22-004G-A57G and SDMX22-004G-E46G. Newroe has one and Brazillian River has the other, but they both look identical. Does anyone know what the differences are?

I could be wrong, but I believe the last digits signify the factory they came from is all. The other numbers are the same so they should be identical.

Thanks for the info!

I never thought a tapeworm could be so useful!