Lamps that are capped with bottle caps have a date printed on them. On 32 oz. globes there are two big numbers printed on the left side of the cap that have the model number on them.
This would mean this lamp is model number: 03 (a white/blue).
Color code # 29
On 52 oz. globes the numbers also have some characters with the big numbers such as "D" and sometimes an extra number in front of the color code, so you might see something like 103D. The code for this would be 03.
Color code # 21
Picture made by Dr. WHAT?!
Very rare or unreleased globes:
See liquid swapping section regarding how to create rare or unreleased colors.