F with unusual track frames coming up for auction

[Blake Malkamaki]

This model F "String of Pearls" appears to have tracks with no "pearls" - and it has lower track wheels. The pads on the tracks look like regular F tracks stamped out of steel. What do you think? Is this an experimental tractor, or is it a recent modification?

http://www.jrauctions.net/servlet/List.do?auctionId=110429&page=info&lotId=36&startLotId=36&direction=next&categoryId=&filter=&showThumbNails=true

Blake