Check to make sure the back block has no wear on the part facing forward. Make sure the spacing when the back block is forward is about as wide as a credit card thickness.
Biggest thing with Autocockers is to make sure the back block is not hitting/making contact with the body. Otherwise the rod will snap.
Other than that, treat it as any other marker and check the obvious parts.
Breach wear, bolt wear, detent condition, eye ribbon condition, etc.