Commander

No caseback is the specification; a screw back is the finding

A genuine monocoque Commander has an integral case base with no seam, no notches and nothing to unscrew. Counterfeits and rebuilt watches are frequently built on conventional cases, so the PRESENCE of a separable back on a watch presented as a monocoque Commander is what should be reported. This inverts the usual expectation and is the fastest check on the model.

Crystal condition carries the service history here

Because the movement is accessed through the front, every service on a monocoque watch involves removing and reseating the crystal. Crystal fit, seal condition and any damage to the case's crystal seat therefore tell you what a caseback and its gasket would tell you on an ordinary watch. A poorly seated crystal on a Commander is both a water-resistance problem and evidence of past work.