My guess is Harold Corkern, helper from the Publishing Committee. He was a Co Host on the August 2015 JW TV monthly program. He's served in Bethel for more than 33 years. In 2012 he was a member of the US Branch Committee. He was also President of the Kingdom Support Services Inc (2000)
My other guess would be Mark Noumair He co hosted on the Dec 2014 JW TV monthly program and presented as helper from the Teaching Committee. Apparently he worked at the Kenyan Bethal in the mid 80s as a missionary. He is a Gillead Instructor and he is mentioned a lot in JW publications.
It is because these guys have been privileged with Co Hosting on a Monthly TV program that I base my guess on. I can't think of a more prominent position other than presenting one of these programs as the Host.