Detect Missing Records in Dataset
One option is hashing, assigning a numerical value to each widget. The best hashing option is if each widget had a unique id, something like a serial number. If a widget does not have inherent unique, then a hash value can be created by applying a hash function to the features of widget.
After creating hash values for each widget, set comparison can be used to see if any hashed values are different between the two sets of widgets.