A co-worker recently asked me if the following is a good way to identify objects in Drupal 8:
get_class($object) == 'Drupal\Namespace\Thinger\ThingObjectService'
That totally works. It's just not very durable.
In Drupal 8, there is a built-in notion that almost anything might be swapped out for a different behavior. Thinger Service is known to be powered by a given class, but that class can be changed. Plugin X is defined as associated with a given class by annotations and whatnot, but those, too, can have their class changed. This means any code that hardwires a specific class has a slight amount of brittleness.