The user clicks on an object ID in the Objects panel on the left and is shown a list of revision dates for that object. Checking one or more dates displays the data for the revisions in the Data panel on the right. When a given key does not appear in a revision, the corresponding table cell is blank. When a value for a particular key has changed from one revision to the next, the corresponding table cell is highlighted in the latter revision.
See the code on GitHub.