We played your game in Taipei the other day! We made teams of 2 people, and played 15 minutes around our location. Every time we found a high number we shared a picture of it in our group chat, to prevent other teams from taking the same plate.
It was very fun for how simple it is! We started going around running a bit to catch parked cars max numbers, but fastly gravitated towards pointing our phone cameras to the rolling traffic on the road
Here in Taiwan most mopeds only have 2-3 letters and 3 numbers, so all high scores came from cars, which have 3 letters and 4 numbers generally. We managed to find a 9956 (!).
We didn't do multipliers because there wasn't so much variation of number plate colours for cars here, and since we played only a short time it was fun enough to go for the highest number, but we thought it would have been fun to also play for the smallest number at the same time we play for highest number.




























