Hi Lynn
I suspect a possibly a typo for T16, but the seller does have some interesting stuff including a FAT post card
http://www.ebay.com/itm/ORIGINAL-WWI...item19d096ecd6.
All my books say a T20 was a Tank.
Cheers Phil
Just found that the same picture is in Bart Vanderveen's Observers Fighting Vehicles Directory WWII captioned Carrier Universal T16