[TimG]

There are lots of ways to tell. Most reproduction stickers do not have the six digit code in the upper right of the sticker. This is an order number and increases as the year goes on. The print of the last six digits of the ID number on a reproduction sticker are different, they tend to be more curvy. The two letter code to the right of the option number really means something. This is, I believe, the ECR or EGR code and ties into a specific option for correlation with other options. U17 "Special Instrumentation" has a different code depending on the engine option even though the U17 code is called the same with a base motor or L78.
Most reproduction stickers do not have the dealer or zone number listed.
Even if you had an original sticker and made a reproduction, the "O" is much more rounded on a reporduction. The "O" on an original is squared off.
The line with the gear ratio has no space between the gear number and the work "ratio".
I bet other members can add lots to look for.
I like to keep lots of stickers on hand for comparison reasons. I am looking at a sticker for my Pace Car and it is Norwood ID number 640491 and order number 323005. A later ID number car should have a higher order number.