Refurbished should mean new rollers, new wire if needed, checked soldering, check windings, etc.
Warranty?
Regardless, I pop them open and do a visual myself. Check for a seal first or warranty may be void if broken. Ask the sender if you can break the seal to look too. (just get and keep corrospondences about breaking seals in case.) (I also check my own oil and lugnuts after serviceing and before I drive off in a new car too. It doesn't kill me 🤔🤔 )
Pull the handles, maybe bulbs, four screws, lift cover.
Mainly check....#1 that rollers are intact and roll WELL, not sliding. (rollers and pins are cheap, maybe a quarter? So always get extras. (kinda easy, but over setting the pin bends the pin, which is also the roller axle, and they don't roll well on a bent axle. They will tend to turn-skid-turn-skid and that wears them out fast if the pin is bent (really just a tall rivet..some folk just use a cotter pin instead.))
#2 The windings show little wear. Every dent, flat spot, nick, or sawing mark takes from the winding wire diameter, which lowers the amout or power it can flow. Lots of wear means less than 180w. No discoloration; applies here below too...
#3 Check the roller arms are not discolored from heat (dark, rainbow or red/blue/black discoloring is caused by excessive heat.)
#4 Closed up, plugged in (use a plug strip with off switch/breaker "in case". A KW can weld.)
Give it power and create a dead short between two posts (A&Com/U). Count in seconds how long the breaker takes to trip an compare it to specs. (4-10 seconds... I forget what the KW countdown is offhand.)
If everything is fine your gonna love the power you have now 😘