Clive correctly points out that a pound weight is lb, not Ib. This lb comes from the Italian "libbra", approximately half a kilo. Originally a pound sterling was the value of 1 lb of silver.
I don't understand the other part of the question. 2.00 pounds is more likely to mean money, two pounds sterling, £2.00, though perhaps an American will correct me as I know that pounds weight are still used also in technical contexts in the USA.