I can't help but notice now that I look at it that the 8D Smelter Droids here are called D8 Smelter. I was wondering if this was some sort of typographical error that got propagated throughout the system or if it was intended. Strictly speaking it is wrong. It would be calling an R2 Unit a D2 Unit.
Below you will find a link to the Wookieepedia page about them, which further links to various other references.