Problems & Puzzles: Conjectures

"Chen's work mentioned in the discussion of the Goldbach conjecture also showed that every even number is the difference between a prime and a P2." Note : P2 is "a number with no more than two prime factors"

(http://www.utm.edu/research/primes/notes/conjectures/#Goldbach)

***

Paul Jobling wrote (20/12/2000): "Chen actually proved this!".

***

Why I posed this as a conjecture? To tell the truth I don't remember now. Maybe because the Chen's proof is only valid "...for every sufficiently large even number...", according to p. 297, Ribbenboim's well known book? Any help from the readers?

***