Ask them to check if there is a label near the power cord, mine has the month/year manufactured there.
For what it's worth, mine was made in 06/2014 and has the 4.0, but I know they made the switch much earlier.
Paragon would probably be able to give you an exact answer
Paragon Industries, L.P.,
2011 South Town East Blvd.
Mesquite, Texas 75149-1122
1-800-876-4328
Fax: 972-222-0646