Margo, a plectrum and a flat pick are the same item. People in the US seem more likely to call it a flat pick where as I in the UK would call it a plectrum or more usually a "plec" - that maybe regional though.

Another device used to play the tenor banjo is a thing called a thimble which is basically a small tube that fits on a finger and is cut at an angle to allow the picking. Tony Sullivan (Sully) mentioned in the other thread used to and probably still does use this device although on the couple of occasions that I have met him, he used the pick.

Jon