Answer to: I bought a used oneI am new at this, but maybe looking closely at the assembly manuals can help you identify which printer you have. I don't really know if other Prusas have a place to load from a USB stick, but mine does not. It is an MK2. If you look through the online manuals you might find some details to show you which model it is. It looks like the 2.85 mm filament version has a printed gear on the extruder which 1.75mm do not have, for the first marker I can find. (Click on the assembly guide marked as obsolete and then look at section 5) For the MK 1, look at the guide that has no "MK" in the title and compare to the "MK2" guide. The first thing I found that seems sort of easy for comparison between the two was section 4, the X-axis assembly. The belt holder looks a little different. The MK 1 is illustrated in step 24 and the MK 2 is illustrated in step 17 (unless an edit to the manuals changes those numbers). The MK2 looks like a little face until you get everything attached to it, not so much the MK1 model. This shoul...