The classification of a composite article depends on which component gives the product its essential character. A lock body with an integrated electronic module may still classify here if the mechanical locking function predominates, but a device where the electronic control is the principal feature could fall under the electrical machinery chapter. A binding ruling from CBP is recommended for smart-lock products.

Yes — subheading 830170 specifically covers base metal keys presented separately (not accompanying a lock). Keys sold together with a lock as a set would generally be classified with the lock under the applicable lock subheading.