Not sure… I tried comparing a bunch of them once, and IIRC they were typically (always?) the same number. I think someone said a long time ago that Game Boy and other systems used them as sort of a version thing… so if a label had 21 stamped on it, it was a v1, 22 meant v2, etc. But as far as I know, there’s not multiple versions of any VB games.
DogP
We could make survey here at the forum.
I’ll update this as others contribute with their findings:
3D Tetris US: 22
Galactic Pinball JP: 23
Galactic Pinball US: 09
Golf (US): 19
Mario Clash US: 22
Mario’s Tennis JP: 19
Mario’s Tennis US: 19
Nester’s Funky Bowling: 22
Red Alarm US: 09
Teleroboxer US: 19
Vertical Force JP: 22
Vertical Force US: 22
Virtual League Baseball US: 22
Waterworld: 22
22 seems popular…
Latest update from jzagal.
On the labels of the carts, they’re mot printed but just stamped in the paper so there’s an indentation in the label in the form of numbers. On the right, lower part on my carts.
Galactic Pinball JP: 23
Mario’s Tennis US: 19
Virtual League Baseball US: 22
Red Alarm US: 09
Teleroboxer (US) 19
Waterworld 22 (same as before)
Golf (US) 19
Nester’s Funky Bowling 22
3D Tetris (US) 22
Mario Clash (US) 22
Vertical Force (US) 22
Vertical Force (JP) 22 (no faint “1” on mine)
The faint “1” on V.F. JP could be the edge of the stamping tool that has left an impression.
I have 2 US Mario’s Tennis carts that are marked 09, and another US Mario’s Tennis cart marked 19.
I can’t update my summary since editing is not allowed anymore but thanks for the update.