What is the difference between Assignee and Current Assignee?

Original Assignee is the Assignee on the Patent (owner of the patent) as written on the patent document. This is true for Assignees that had owned the patent before but no longer own it.

Our Patent Overview lists who originally owned the patent, and who owns it now. This Assignee is called the Current Assignee. We receive official information on assignments from the Patent Office. 

In order to check for records currently owned by an Assignee, you can add the following operator: 

ANC:"company name"

In order to check for records who may have previously or originally be owned by an Assignee, you can add the following operator:
AN:"company name"

In order to check for records who at any time were owned by a specific Assignee, you can add the following operator which will check in all current and original Assignees:
ALL_AN:"company name"